So I'm trying to imagine the main states that could evolve out of this situation. I want to stop both the French Royals or another group (like the Angevins) dominating the place.
Royal domain
Normandy
Brittany
Champagne
Greater Anjou
Aquitaine
Auverne (?)
Burgundy
Gascony
Toulose
and Provence outside the borders
Are these reasonable? Could different cultures evolve in each?
Why "Greater Anjou"? Why not Anjou, Maine, Vendome etc all separately? After all, a great weakening of royal control and the establishment of the various royal vassals as semi-sovereign subjects is going to encourage any lord with no direct liege between himself and the King to flaunt the new opportunities. I doubt you'll see smaller counties spontaneously blobbing together, and I doubt that there will be much annexation of the weaker, as too many of the newly-powerful lords will appreciate that accepting wanton warlording and dominations of the weaker lords is the way to allowing one Duke to eventually grow powerful enough to seize the throne - there were enough large Duchies in France already. Most likely the aspirations of all but the petty lordlings would be blocked by the rest of the electoral college.
Also, Berry, Bourbonnais, maybe Foix asserting itself in time, Orleans (depending on the time period, I guess)...?