I would love Civ VIII to take heavy inspiration from Age of Wonders IV. It uses a character creator for its Leaders and Heroes (who serve as Commanders, Governors, and Great People all rolled into one, as Civ should do).
Civs should be classified as belonging to one of a few broad Culture. These in turn would determine what customization options are available when making a Leader for that civ. If you’re playing an American civ, you could choose from tons of awesome feathered headdresses, with more unlocked as you finish goals and games. Asian civs in turn would get cool samurai armor; Mediterranean civs Greco-Roman togas; European civs knightly panoplies; etc. And of course some gear would be common to multiple or even all Cultures.
Future expansions, instead of adding new Leaders, would add new leader traits, new Cultures, and new gear pieces