And to run it forward that 100,000 man army needs to eat every day and requires food or money to buy food and in general oppresses the the local population dispersing as they eat out each region and without a corps of officers able to keep order degenerates into roaming bands of pillagers and get screwed over when a disciplined army fetches up up. And that might be a part of Wallenstein's army that keeps its discipline.
Of course, discipline of Wallenstein’s army was low but it was not lower than in the most of the contemporary armies and his system of getting money from the German stated had been working when he was in charge. And as long as the system was working and the troops had been paid with a reasonable regularity, the discipline was not deteriorating below customary level. I have no idea where did you get a notion about an absence of the “corps of the officers” but what you are seemingly missing is that Wallenstein’s system was based upon the regulated money extortions on the state level instead of a chaotic looting of a territory.
Oppression of the local population also was a standard practice of the time and at least he managed to avoid excesses like the sack of Magdeburg or the Swedish
intentional campaigns of terror used by the GA and his successor-commanders. Take, for example, Mecklenburg. While Wallenstein was its duke, he improved administration and economy and even introduced a law for helping the poor. When it was occupied by the Swedes, they launched a campaign of a terror to “punish” the dukes. The Dukes survived but population shrunk from 300,000 down to 50,000 and, according to the Swedish fieldmarshal Banner, “Tyere is nothing left in Mecklenburg except sand and air, everything is destroyed to the ground”.
Neither Wallenstein nor the Hapsburgs of Austria have access to the New World gold and silver they can throw at the army periodically to keep them in line.
This is a theory but practice was different. The
Austrian Hapsburgs had been relying upon the Spanish subsidies for most of the war but Wallenstein did not and it seems that a considerable part of the money and military supplies that he needed was coming from his estates. He was seemingly a very good administrator, which is more than can be said about Ferdinand.
Now, Spain did have all that New World gold and silver and more often than not it was incapable of paying its troops and went bankrupt, unlike the Netherlands which did not have a bullion coming from the New World of France which also did not have an access to the overseas precious metals but managed to subsidized the anti-Hapsburg forces while also dealing with the serious domestic issues.
The problem with unifying the HRE is that several other people have no interest at all in a strong powerful HRE ruled by the House of Hapsburg ( or anyone else) including but not limited to the Princes of the Empire, France, Poland, the Ottomans, The UP, England every other Monarchy in Europe, the Pope.
Princes of the Empire had been, before the “Swedish stage” of a war, reasonably subdued. Of course, not up to the level of having a truly unified HRE but to a degree making Ferdinand a clearly top dog. Position, which he immediately abused with the insane pushing restoration of the positions lost by the Catholic Church.
France
was a major problem but (a) until the last stages of the 30YW it did not have an army capable of a serious intervention into the German affairs and had rely upon the subsidies paid to the 3rd parties and (b) in practical terms, it was more concerned with fighting Spain then messing i the HRE.
Poland as an opponent of the Hapsburgs is something new to me. In OTL the imperial troops (under vin Arnim) participated in its war against Sweden. In the practical terms, the PLC as a major factor capable of serious interference into the 30YW did not exist. It could not even kick tye Swedes out of Livonia and it’s main interest was on the Eastern borders (Smolensk War, fighting the Ottomans, war with sweden ).
The Ottomans promised to interfere on the early stage of the 30YW but limited their involvement to the Transylvanian troops and went against the PLC (Hapsburg ally).
The United Provinces had been busy fighting Spain.
England of Charles I was a joke: under the leadership of the Duke of Buckingham it was moving from one embarrassment to another.
Spain was an ally.