I love the idea of having Leaders and Civs to be separated. The gameplay variety it provides is fantastic.
However, I struggle to remember who is which Civ, and you can't see it at a glance too.
Thus, I'd love for each Leader to get an appropriate outfit for their current Civ. It would be much easier to remember that Napoleon in a Mayan outfit is the Mayans. On age transition he would change to a new outfit reflecting the new Civ.
I know it's not an easy ask, but I think it is within reason all things considered.