I doubt such an occurrence is likely. Even if the Hugonids take power, Frankland would be such a fuedal mess that such a swift consolidation is unlikely.
Francia was not feudal mess, because of the absence of feudal system. The Hugonids and Peppinids were closely related, and with the disapprence of the last great Peppinid figure, they will "inherit" of the ties with others families and more importantly, of the great gallic domains.
These domains, unreachable for Muslims raids, are enough to use the gift-based microeconomy and to control really quickly all the Austrasia.
Theire issues would be (in order of importance) 1)Neustria, 2)Bavaria 3)Alemania.
For Neustria, they have a choice.
-Allow Aquitaine to remain independent, at last for a time, and to recognize them the royal title that the Neustrian gave them in 717. It's dangerous to make a state that have a real support of nobility and a relative stability, but it would allow to take control of the weak Neustria in two years.
OR
-Attack Neustria, no matter the Aquitain help. As they will be busy with the Muslims and more weak (the 732 raid was all about Aquitaine that was ravaged). It's a non negligable chance to end all of this quickly. But they'll be forced to deal sooner or later with Aquitaine as Charles Martel did OTL.
For Bavaria, it's quite difficult. After all the duke in place was tied with Pippinids, and more or less put in charge by them. Bavarians nobles could be tempted to have since 732 an independent existence (they tried to do so OTL). They're not really dangerous, but the traditional Aquitain-Bavarian alliance is, because it forces Franks to deal with two fronts at every war.
So, or they manage to buy Bavarian nobles enough to settle a new tie, or they strike right after the first tentative of autonomy. Again, a harshly weakened Aquitaine which have to deal with Muslims is a bonus.
Alemania is quite supportive of Hugonids, but it would cost more protection and more efforts that Pippinids give OTL. It would maybe force Austrasians to let some western possessions slowly shift from Frankish Kingdom (Brittany, North Aquitaine).
Regarding Provence, it's more complicated. They have claims to intervene, and they could be called by some patrices in opposition with Abbon (critically if they reinstate a merovingian king). It would be a real bonus to take Septimania. But except that, it's not a great deal to take this land, when they can took Frisia which was as rich, and not at all regularly subject to Islamic raids and piracy.
Point two is dependent on the soundness of point one, and your point one is shifty at best.
I suppose you used the word for "evasive"? I would be interested to see your points about why Austrasians nobles wouldn't follow the Hugonids if they manage to hold their domains + the ones of Pippinids.
There was much more at stake in 732 than 721...
No.
The 721 was a conquering expedition with infantry, war machines for sieges, families.
Not only 732 was only a raid campaign, not discernable from 725 one that reached Autun, but the only battles that are sourced by more than two islamic scholars are Toulouse and Narbonne.
The numbers given for the Battle of Poitiers are totally imaginary, given centuries after the Battle (the chronicles of the VIII don't mention any number, and hardly mention the battle if you except the chronicles payed by Peppinids and Carolingians).
Why Toulouse and Narbonne are more present in Islamic sources? Because they were real defeats that stopped Islamic progress in Europe.
The Battle of Toulouse was the point where Muslims stopped to plan conquest north of Spain (no one more was made) and the loss of Narbonne meant that they won't be able to make raids in Gaul that provided them many richess.
It's really not. Your basing your assumptions on ties and opportunities that aren't present to the Franks at this time.
Which ones?
A decisive Muslim victory would mean a foothold in southern France indefinitely.
Muslims don't have the forces to do so. North of Pyrenées in 731, there's only the garrison of Narbonne/Arbuna.
In the iberic peninsula you have at maximum 4,000 Arabs, 15,000 Berbers.
It's okay for keeping control of a region which have hardly 3 millions inhabitants, but not for a region (southern Gaul) which host the majority of the 8 millions of inhabitants the Gaul had.
I repeat, and it's sourced everywere, except Narbonne, all the land under Islamic rule was directly ruled by Christians and because of that, conquest of Septimania, except Narbonne, was a wealthy promenade for Franks OTL.
At this point, it's a race who can convert the Germans first.
Massive conversions in Muslim Spain didn't happened before the second part of IX and when it happened, it touched mainly the south, while the North hosted a majoritary Christian population.
By taking -again- the exemple of Septimania, it's no trace of an important noble that converted himself (at the contrary of Spain, when you can find the Banu Qasi by exemple). Even Ardo (who was probably the last king of Goths, only under Islamic rule) didn't converted.
Furthermore the massive conversion movment in Spain first concerned the slaves that were more present in Visigothic Spain than everywhere in Western Europe.
The Franks will not risk such a military campaign with hostile and quite frankly (lol wordplay) more powerful and experienced forces to the south. The lombards are pretty much out of the equation as well.
Frankish warriors are really experienced. Not only they manage to conquer Frisa (that are hardly the barbarians described in the chronicles, at the contrary), but they developped new techniques that allowed them to beat the light cavalry of the Gascons and at Poitiers OTL, the Islamic cavalry.
Heavy cavalry and mounted infantry are present since this period.
More powerful? Muslims in Spain were totally divided and a state of civil war will last until Abd al Rahman I in 750's, and even there, many Muslims wouldn't recognize his rule.
Muslims were divided, beaten many times (Toulouse, but not only) and Franks are totally able to do that, as they did OTL. A single battle and the death of Charles Martel is not going to change that.