Weird thought I just had in relation to that: I think we should bring back, sort of, the Civ II concept of the Ambassador (who, in Civ II, was the unidentified foreign-clothed official who visited you on the diplomacy screen).
In this new version, the Ambassador is the 3D personification of the civ whom you interact. Unlike Civ II, ambassadors should be based on actual people, personification or mythological figures representative of that civilization. They could be political leaders, but, since the whole point is that the ambassador is separate from the leader, they wouldn't have to be - Elvis could finally make his return to civ as the American ambassador, for example. Or it could be Uncle Sam. And we coudl park Gandhi here where he can still threaten people with nukes and keep the meme fans happy while having actual Indian leaders lead India. These ambassadors might well never be refered to by name - they could simply be displayed as "American Ambassador", "English Ambassador", etc.
The leader - (maybe call him a Founder instead?) -, meanwhile, would be represented in a much less graphic-intensive way (an icon of some sort, perhaps), but otherwise function as the leader in Civ VI, granting abilities and tweaking the AI (in subtler and more reasonable ways) of their civ. The less intensive requirements of new leaders shoudl allow for additional leaders and thus alt leaders for more civs , and possibly open the door for game modes relying on the existence of alt leaders.