[HoneyBadger]

Or, maybe on a larger (1500 province) map, at some point adding in the middle, and then the later era nations, on close by provinces, while still keeping the original ea nations, and making those middle and late nations allies to their ea nations, atleast to begin with. This would not only simulate growth and diversity, "new blood": new strategies and techniques for old nations, but also the potential to "split off" into separate colonies, which may become independent. It would also make huge maps more interesting to play. This could later be expanded to include modded in nations, for the sake of interest and diversity-for instance, if a province formerly occupied by independent cavemen suddenly transformed into a strong Ogre Kingdoms nation on the 50th turn and started taking the piss out of you.

If the human-played nation or nations in the game could come to control their middle and late eras, as close allies, that could also be a lot of fun.