For future versions they could include cities making revolution, founding a new country in game, etc.
Another thing would be the named barbarians like "huns, assyrians, etc" actually occupying a city, and founding their own civilization, also with data characteristics, the assyrians would be militaristic and expansionistic for example with 100% of aggressive behaviour in the case their barbarians occupy a neighbouring city. Too many civs disappeared and were formed in this way. The Assyrians took over from the Kassites who invaded them by using the iron weapons the Kassites introduced.
But maybe it would need a more advanced game, and computer, to handle 100 civilizations at least. That way would be realistic, and you would start with the ancient civs from the 3500 aC, Sumer, Egypt. And the rest would be nomad barbs with an identity roaming the lands of europe.
Another inclusion should be language classification.
Alphabet also should come after Writing, and should allow a faster science, and also Literature spreading to common people.
Maybe there should be social differences also, commonners, priests, slaves, etc for the ancient.