Agreed on all points, I like how much is changed depending on whether a Spanish or Portuguese match occurs.
Something else to think about is the effect on Spain's war with the Dutch. OTL Madrid's terrible relations with England and France forced them to rely on the Spanish to send troops to the Netherlands. A route that was later closed thanks to the French and Savoyard alliance. Here, with an Anglo-Spanish alliance in place the sea route could be re-opened, allowing for much quicker and easier reinforcements to arrive from Spain. It could be a full naval route from La Coruña via the English Channel to Dunkirk, Brugge or another Flemish port. Or it could go La Coruña, a landing in maybe Bristol, a march to Dover and then sail down to the Spanish Netherlands. Either way it decreases the strategic importance of the Savoyards and Swiss and increases English influence without direct intervention.
Could you point out where you have GA2's determination to intervene from? As I have mentioned earlier, Sweden can't really intervene unless both Russia and the PLC are occupied. IOTL this happened in the Smolensk War as a result of negotiations between the Sweden and Russia, which were pushed along by Richelieu.
I honestly think you can keep Sweden out of the 30YW if you disgrace Richelieu, either delaying or preventing the Russo-Swedish negotiations. If you can delay Swedish intervention for a couple years then it becomes too late to really intervene in the war, and more profitable to focus elsewhere. Sweden really doesn't have the resources to intervene in Germany unless they get the french subsidies, which are also tied to Richelieu.
The Imperial conquest of Stralslund would have several interesting effects, particularly because it signaled the end of Wallenstein's string of victories IOTL and the beginning of his fall from grace. Without the loss at Straslund Wallenstein remains one of the strongest actors in Germany and leaves Ferdinand without any reason to dismiss him. I think you might end up having Wallenstein take his place as a major player within the HRE power structures though I doubt he would directly challenge Habsburg power.
The loss at Stralslund does create serious issue for all actors in the Baltic, but I have a hard time seeing how the Scandinavian powers can really do anything about it. They may very well push for Stralslund to go as part of the Pommeranian inheritance or that it remain a free city. I think the second of those options the more likely, because it would be very hard for Ferdinand to truly challenge. If he starts mucking around with free city status and claiming free cities he may very well turn the free cities of Germany against him.
Same source I'm going by for most of this:
Thirty Years' War: Europe's tragedy. I haven't got to the Swedish intervention yet (just finished part one and am at the start of the Bohemian revolt) but from the parts I've read ahead on Gustav had wanted to get involved in Germany from at least 1627, maybe earlier. Oxenstierna had to persuade him to finish with Poland first. Later in 1630, before his landing in Pomerania, he engaged in more or less fake negotiations with the Habsburgs to force France to make a better offer alliance to him. Clearly Sweden's King was going to intervene in Germany with or without French aid: Richielieu didn't turn to Sweden until 1629 and after Lübeck, a full two years after Gustav's first mentioned desire for a German war. As to Russia, that part I don't get. Russia and Sweden were at peace from 1617 until 1655. I doubt Russia would launch an attack on Sweden during her German intervention due to the fear of a Polish attack while Moscow's forces are focused in Livonia and Ingria. So you might be overestimating Russia's potential role in all this.
That's similar to what I was thinking as well. Wallenstein here is the hero of the Empire and Catholicism, the man who's restored imperial rule in the North for the first time in over a century and has pushed imperial power farther than its been sense the Hohenstaufens, if not the Salians. The Prince-Electors wouldn't have the excuse or backing to convincingly push for his dismissal and Ferdinand has no reason to cave to their demands. And I agree: realistically the fear that Wallenstein would challenge Imperial power was fantastical at best. He'd definitely be a major player in politics and might act more autonomously than the Court of Vienna would like, but he's no threat to Habsburg dominance, if only because he'd never get the necessary support from the other Princes to do so.
As to Stralslund, I think making it a free city makes the best sense. It detaches it from Pomeranian and Brandenburger control, preserves the city's autonomy and places it under Imperial purview. Of course, considering the city's importance and resistance to imperial forces, I think its government would be gutted in favor of Imperialists and have to accept a permanent garrison.
I think this sounds very interesting, though I would like to remind you that a reason for Protestant dissatisfaction with the Habsburgs was that the Habsburgs demanded aid against the Ottomans in the Long War. I think a Army of the Empire under the Diet, subdivided by Imperial Circle is likely to be the most palatable solution for all parties involved.
From what I read in
Thirty Years' war that's not entirely true. The Palatinate and its allies kicked up a fight over war with the Turks but most other Protestant states, including Brandenburg and Saxony, had no issue with voting subsidies for the war or sending troops. In fact there's a hole chapter on the subject. Basically a war with the infidel Turks was considered one of the only things that unified the confessional sects of Christendom. As for your idea, that's basically what existed OTL. I think it would remain similar but more expanded and with key strategic points (like the border or say parts of the Palatinate) garrisoned by the Emperor. Its in favor of the Habsburgs but still a compromise.
On Iberia and the influence of Dutch financial systems on Spain, I want you to take a moment and consider the PoV of the Spanish at this point. They have just defeated the heretics they have fought for the last century, I doubt they would be accepting them as part of Spanish high society or as part of the bureaucracy any time soon. I think it is more likely that as the Spanish and German Habsburgs start to strengthen their grip on their territories you will see a steady stream of refugees into Huguenot France, England/Scotland and Scandinavia. The fall of the Netherlands would be like a second fall of Constantinople in many ways, though likely with far more people involved.
I doubt you would see something like the Nueva Planta decrees since that simply wasn't part of the Habsburg way of rule. The Habsburgs were always rather adept at playing the numerous crowns and lands against each other for their own gain. The Bourbons brought with them the centralizing zeal that was instilled from Henri IV onwards. Each Dynasty has a couple of traits that kind of characterize them, with the Bourbons it is centralization while with the Habsburgs it is a tendency to function well in complicated and intricate realms they tied together through marriage. This is a broad generalization but it is a trend I think you can see throughout most of either family's rulers.
What are the likely butterflies from a Spanish match and how does it affect the Civil War in England? A victory in the Anglo-French war might also have significant impacts. Would we even see a Commonwealth appear by this point in time? Would royalist/parliamentary forces act differently if they had more experience from a longer and more successful war?
A last thought. If England aided Spain against the Dutch, would Dutch Calvinists flee to England? and what would the effects be on their coreligionists in England at this betrayal of the faithful?
I think you might be overestimating things in regards to the Dutch. I mean yes Spain has spent the better part of half a century at war with the Dutch, but the Spaniards aren't blind to the dazzling success of their enemies financial system. Now that they've retaken control over the Netherlands there's no reason to not attempt to copy the system for Spain. After all, money and power are very attractive and I can easily see some of the Dutch willing to play ball with the Spanish. At the least Olivares and his circle would see the value of co-opting their returned subjects into Spain's empire. It probably wouldn't be popular, but necessary. Though on the flip side Spain would control the Dutch financial system, their wealthy trade lines and the East and West India companies. Reforms might not be as necessary if such wealth is under Madrid's influence, if not control. The financial changes alone would be fascinating to explore.
As to massive immigration, that would likely happen initially but not long-term. Look at Spanish religious policy in the Netherlands from the Archdukes onward. It was basically similar to that of the French towards the Huguenots after Richelieu's centralization policies: tolerated as long as there was no public worship. It wouldn't be popular in the North but much better than they feared. Plus I wonder what the population percentage of Protestants and Catholics actually was in the Republic at this time. I know that a lot of the rural population remained Catholic while the towns and cities were Calvinist but that's it. Not sure which had the larger population or by what percentage. As for refugees, it depends. Strangely enough there was tons of infighting between Lutherans and Calvinists during the era leading up to the War, almost more than between the Protestants and Catholics. The Lutheran states and England might be reluctant to take in too many refugees of a different religious persuasion, especially ones that could cause problems in their new countries.
To Spain's domestic woes, your probably right about no Nueva Planta but I do think we'd see the Aragonese lose some of their autonomy, especially in regards to taxes. After all the lands of Aragon payed practically nothing in regards to taxes OTL. Here they've revolted and been defeated: no need to have a status quo peace. Aragon's gonna be made to pay their fair share. IDK if it would be up to the Castilian level of taxes but certainly a few perpetual taxes outside of the estates' control. We could also possibly see Olivares' union of arms plan successfully implemented if the Aragonese estates are weakened. That in itself puts Spain on a much stronger military footing. I mean being able to realistically field a standing army of 140,000? It practically guarantees long-term Spanish success.
Of course I'm still unsure about Portugal. Clearly Portugal would be a hotspot in terms of tension and could potentially still revolt, but not entirely sure on the details. I had thought of having Infante Carlos (Felipe IV's brother) survive and take up his designated post as Viceroy in Lisbon, later leading the Portuguese to independence in a way not dissimilar to Pedro I in Brazil but he could just as easily be used to ease tension and bring about a closes Iberian monarchy. I'll have to work on this one.
England's gonna be a tough one to figure out. For one Charles's reign starts out with a major foreign victory, even if its not the one the militants want (restoration of the Palatinate). This, combined with the lack of Buckingham, means Parliament has no real leg to stand on to deny Tonnage and Poundage to the King. That in itself reduces some of the drama that dominated the early years of the reign. That being said, its a temporary band-aid at best. The issues between Crown and Parliament went back to Elizabeth I's reign and Charles had the luck of being the wrong person at the wrong time. Of course his willingness to fight fire with fire caused its own problems and I won't say Charles was merely the victim of circumstance, but the blame isn't entirely on him. Something else to consider is the massive Spanish dowry. At £600,000 it would be the largest one in English history (even larger than Catherine of Braganza's in 1662), a massive boost to the Stuart monarchy. Hell a smart move would be to use some of it to buy back lands from the nobility and increase the size of the crown estate. That would lessen the dependence on Parliament. Basically Charles would be dealt a much stronger early hand than OTL.
As to the civil war, harder to say. Conflict was inevitable but a full blown civil war was not. Maybe Parliament is easier to deal with without multiple defeats or just as easily Charles uses his victories as an excuse to rule without Parliament. Now assuming a civil war still happens, Charles is again stronger than OTL. He's closely allied with Spain, whose won in the Netherlands and has no obligations in Germany (not sure about a Franco-Spanish war though). Thus he can reasonably call on Spanish troops to assist, along with Spanish subsidies. Spanish veterans at the core of a Royalist army could make a big difference, not to mention we could see the English veterans side with the King and not Parliament. In all I'm not 100% on whether or not a civil war would still happen, but if so I think Charles stands a good chance at winning.
As to Dutch refugees, hard to say. While we'd probably see some refugees go to England and Scotland, I imagine Charles would want to limit them. No need to potentially strengthen the Puritans or other Calvinist leaning sects in England who are opposed to Royal policies. And yeah the English Calvinists would be pissed but they're still going to be excluded from power so long-term all they get is another propaganda piece. Hell the fall of the Netherlands might be popular in England among certain circles as it means the English can brake into the Dutch trade in the East Indies. Just a thought.
The problem with having the Habsburgs retake Hungary is the same as during the pre-30YW period, If they move their focus south-east then they lose their grip on the north and west. The constant struggle of the Habsburgs up till 1648 was whether to focus on their German vassal states or to focus on their own empire outside of the Empire. If the HRE starts a centralizing process I have a hard time seeing the Habsburgs being able to justify conquests against the Ottomans to their vassals. This would bring them back to the position they were in before the war.
I actually think you might be able to improve the situation in the Ottoman Empire, is there a way of getting the Ottomans to end their practice of driving each other mad? If you can have a strong Sultan emerge at some point, maybe have Murad IV be more willing to compromise, maybe cut down on his brutality somewhat, and escape his death by cirrhosis i think there is something to build on. TBH I don't know too much about the Ottomans at this point in time, but I think there are a lot of opportunities hidden in there.
The more that I've thought about this I think your right. I don't see the Emperor starting a war but at the same time, if a situation like the siege of Vienna happens like OTL, I also don't see the Habsburgs making peace if they're successfully liberating Hungary. Sadly I don't know much about the Ottomans during this era, so I'll have to look into it for the rest. Though I do know that on the whole it was quite unstable (like three or so Sultans were deposed during the course of the Thirty years' war). Maybe Osman II pulls off his plans against the Janissaries?