For example if we take France, do you expect the Napoleonic wars to happen ? If the answer is yes, then I'd suggest totally redesigning France and would suggest some Victory Point/s relating to that, if no then their existing design is probably fine.
no, not to that extent
As a bit of a side thing, I used to find it strange how Aztecs/Inca basically don't interact with anything for a long period of time. I don't know if you can make Mexico big enough, but was thinking maybe including Tzintzuntzan as an independent to spawn alongside the Aztecs. Assuming the Aztecs retain some benefit from a killing units mechanic, then as the player you have a choice of whether to conquer Tzintzuntzan or farm their units.
I checked the location, but Tzintzuntzan is literally 2 tiles from Tenochtitlan
excellent question, I never understood that