Perhaps this is going outside of the topic for this thread but wouldn't it be cool if your leader changed with the eras?
Good luck then with civilizations that are fairly young or very ancient (and ended in ancient era) - now let's invent seven leaders, per each era, for Sumer, Aztecs, America, Mali and Brazil. No fictional leaders or civ switches allowed
I could never understand this recurring idea of changing leaders/civs. It fails even if you want 'oh, just any seven leaders, not chronologically from different eras' because many civs didn't have seven leaders qualifying to be in the game over their entire history.
Aztec/Mexico
Aztec Empire has absolutely nothing to do with Mexico.
Carthage/Morroco
Morocco scending from Carthage makes exactly as much sense as America ascending from Maya.
Vikings/Sweden
Sweden is not the successor of Vikings.
HRE/Germany
HRE didn't consist only of Germany but also of Bohemia, Austria, Netherlands, Flanders, Burgundy and Northern Italy.
Rome/Italy
Roman Empire has nothing to do with modern Italy.
Greece/Byzantium
Ancient Greece has barely anything to do with Byzantium, if anything it'd rather be Rome->Byzantium but even this would be a bad idea as those were two very different civilisations.
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Back to the main topic, I'm 90% sure civ6 won't have multiple rulers per civ at any point of its history (dlcs included) because multiple animated leaders are not worth making instead of entirely new civs, and devs stopped saying about 'leaders abilities' when they realized these words are commonly interpreted as multiple leaders. Besides, such major feature would have been advertised very early.