Or at least different iterations of the same Civ.
For example we have done the Augustus/Trajan/Caesar Rome with the Legionnaires, so next do a Rome from Auerelian or Diocletian where it's heavy cavalry based, with gameplay elements based around using military force for loyalty or something. I'd love an Aurelian based Rome, with his personal ability being based around religion, and his personal UU being a knight replacement. Just to keep it fresh, especially when there are Civs and Empires that have such a massive time frame to be picking from.
We have this now, in the Modded Civs.
For examples, among both 'regular' and Mod versions, in Civ VI we already have 5 different versions of China, 2 versions of England/Britain (and separate Anglo-Saxon and Briton Civs with 4 different alternate leaders among them) 6 versions of France (including leaders as diverse as Charles De Gaulle, Henry IV and Charlemagne), 3 different Germanies, and 2 different Tibets. Given a well-thought out 'framework', the Mod Community can provide all the variety within a Civ in the form of alternative Leaders and Attributes you could desire. The only thing lacking (and to me it is Utterly Unimportant) is animation for most of the Leaders.
. . . If only their language were better attested.

(As I understand it, their nominal morphology is pretty clear, but their verbs and syntax are utterly opaque.)
I have posted this before, but while I love the effort put into getting something close to proper language and dialect for the Leaders (even when they don't quite get it right, I applaud that they are making the effort!), the fact is that it is completely irrelevant to the play of the game, and should not be a complete barrier to including a Civ. As long as a City List can be formulated and peculiar specifics of the Civs' physical, political, military, religious or cultural identity can be identified, there has to be a 'work around' for the language that the Leader is speaking.
Shucks, we could just have the Leader standing in the background gesturing, and an obsequious/imperious/devious-looking Interpretor standing in front speaking the player's language with a weird accent. . .
Given the number of intriguing Civilizations that have had to be 'written off' because of language (Etruscans, Minoans, Olmec, just for three) we need to find a way around The Language Barrier..
(And yes, I know that a City List for the Olmec is currently virtually Impossible, but the etymologists have found Pre-Roman, Pre-Greek place names all over northern Italy and Greece and Crete that can be used for the others, and I am the Eternal Optimist in that there is no telling what the archeologists may dig up tomorrow: an Olmec version of Strabo's Geography or a Grand Tour Itinerary for Olmec cities, for instance. . .)