You won't be able to force it with stabhit.
Can you elaborate?
- you can send such demand at -3 stab and AI will refuse
or
- you can send such demands but there wont be stabhit?
It seems to me that you imply that there still will be stabhit (and it might be even easier to accomplish due to new rule), thus "France" can try to break "England" by rebels occupying e.g. Calais for 20 years.
Edit: and it is not only mine opinion, that demand to release countries without occupation is plain stupid
Additional issue: not all provinces will have forts (from DD). And IIRC Johan said that in 1444 France will have something like 4 forts only, partially due to the maintenance cost.
Does it mean that France (with no navy) can still force England to release vassals on isles? (how many forts will have England? In London I guess, one in north (in northumberland?), maybe in Meath, probably 2 in France (Normandy and Guianne), what about Calais? Will it have forts in Corwall and Wales as well?