You're making a great mod here!!! Joined partly so I could make some suggestions.
In no particular order:
Another independant city needs to spawn in Scotland or Ireland. Otherwise it's just composed of just 1 barb city which is too easy to capture. Also the barb stacks seem to "dissapear" when I move my troops there. How?
England needs a tech boost. The AI never gets to Divine Right fast enough to build its wonders (and also to counter my stronger Scotland/Ireland suggestion). Spain got to Magma Carta and Westminster Abbey before England even got the tech in my games. Letting them start with Cartography also makes sense. The Normans were good explorers right?
Again, Gusiarmiers need to be even with Knights. I suggest giving them +100% vs heavy mounted.
Arabia doesn't spawn often enough, and if they do, don't have enough troops and collapse easily. As a result, France or Germany keeps Jersualem forever.
Cordoba needs a tech boost as well. It never gets to Patronage by 1300 and thus European civs build their wonders. They also need to be more unwilling to vassalize. They always capitalate leading to them becoming a rump state in southern Iberia that never goes away.
Can you make the Dutch have better culture? They always lose their borders over time it seems.
Can Sweden's flip zone be extended east to the western tip of Finland/Estonia? They never expand that way, going after Norway instead.
Norse never settle Iceland, and to be frank, it's a bad spot due to no contact with the mainland. It would be a bad idea if not for the UHV. Can they have trade routes over ocean as well?
Bombards/Great Bombards are too weak (or Longbows are too strong). Against a Longbow with CG3 on a flat city (with a CR2 bombard) gives ~3% odds. I threw 4 at a such a Longbow and it did not hurt it for one decimal point! Give them an additional 25% city attack should work.
Can we make Arbalests not obselete with Longbows? They were still in use in the late middle ages too.
I think they should have 7str, +50% vs melee/polearm, +25% vs mounted, 1 first strike. I also suggest making archers 4str, but only +25% city/hill defence to give them a less restricted role.
A lite version would be a great idea; twice the game crashed while I was saving.
In my opinion, SOI style corps would be better. Often the corp arrangements make no sense. In my latest game, Hanseatic was founded by a lake in the middle of Europe (couldn't spread), the Knights were all in Northwest Europe (Germany, France, and England all founded one near their capital) and never spread to the Med.
Keshiks never get to Bulgaria, Hungary, and Poland. A second wave should spawn (not west of Rus, but to the north or east, so if Kiev is still alive they'll get another wave; otherwise they'll travel further west) I've seen Poland/Lithuania lose a city or too when I placed ~12 extra keshiks with WB after Kiev died, so they will go west if enough spawn.
I apologize if this seems too demanding. Feel free to comment about my ideas, the goal is to make the mod more balanced and enjoyable.