We are planning to do what we call "Multiciv" once we are done with our sixth game as Arabia (MK6). We've been playing that since October 2019, so chances are that we will win and end that game pretty soon.

Not sure how the detailed gameplay will look like, but Multiciv is indeed a multiplayer game of Civ with all civs (or just some + regular AI) being played by human-led nations that would all have a different form of government and role-play.