Alorente
Warlord
It seems that the better idea wouldn't be to tie in geographically close areas into Empires but to make leaders of geographically close areas eligible to become the next leader in the Dynasty of the empire.
That is another great way to approach it. Picking a leader from the eligible candidates that would most benefit the Empire in that particular moment in history. I think you have you've hit on something that could add even more strategic value to the game than what I was envisioning.
Ideally, the change of Era would trigger the election of the new leader by the player. Very good idea Sonereal.