Fullscreen_Lurker wrote:
I'd still like to play as single nation for the entire game from start to finish, shifting between cultures that were part of it's real life history.

Check Gedemon's True Culture Location mod on mod.io. It has Settings that force you to picos cultures that lived in the area you control or transcend 

I wouldn't mind if that would become a side-effect of having many cultures already in the game, like you can kinda already do with some cultures with minimal stretching and transcending, but I'd definitely not like for it to be their DLC philosophy, we'd be missing out on unique cultures that were lost to history and some 'recent' upstarts in exchange for something I fear would end up being quite homogenic.