Played England. Worked fine. I liked the extra barbs in Scotland, but I would prefer that they came in groups rather than singly, to make them more relevant. There's enough room for them to found a city way up North. Perhaps greater instability for English-controlled cities up there (??)
Calais should really not revert to England early on. Historically, that city was captured after a siege. All the others (in Bretagne and Aquitaine) were basically inherited or gained through marriage, which of course would be difficult to emulate with basic CIV mechanics. It makes more sense for cities in Bretagne to revert to England instead of Calais.
I wonder if a *marriage* strategy could be duplicated with python-driven events. I'd hate to see too many cities gained as a result of marriages, but that would be more historical. This idea in fact might be used with other provinces as well (essentially medieval western European) to reflect the feudal idiosyncrasies of the time. Obviously England and France are good examples, but I should think Austria might be another candidate (Hapsburg-style of course). This would only work with Christian feudal monarchies (republics & such are definitely out). Religion becomes a key issue here. Sounds like a project on its own.
Anything like the above should be very limited and not an automatic success (let the player pick the bride/province, with the greater the province the less likely the inheritance odds, etc). Some kind of trade-off would be required, along with an automatic war with the previous owner. This opens the possibility of earning neutral, minors, or even barb provinces...
Might have to ship out either the bride or the groom (GP units) for the marriage to take place (could be physically intercepted by an enemy?) Some techs could address issues like Salic Law, or laws that prevent a kingdom from being divided between heirs, etc. This may be yet another manner in which to catch the AI flat-footed. Definitely pie in the sky, here!
Anyway... cool mod, even without any wonky feudal marriages.