Empires almost always were both. But more importantly, we are talking about "empires" in the Civ VI, 4X gameplay sense, and whether a proposed civ's history syncs with an expansionist attitude.
I never said it was strictly limited to conquering. Wide also includes settling. It's almost as if you didn't read my post at all.
No, but how the player shapes their core empire certainly adds to ludohistorical resonance. Players look at Russia's larger city tiles or Japan's close-knit districts or Spain's colonies on other continents and think "yeah, that feels right." It's why Venice felt like Venice in V, it's a large reason why Scotland doesn't feel like Scotland in VI, and it's why a Haitian empire practically demands a tall playstyle because its imperial effect was cultural, not territorial.
While I agree that Haiti "has a shot," I still generally disagree with the unsaid assumption that VI's overall design sensibility is unchanged from V, which had Venice, and could accommodate Haiti. So far the "smallest" civ we have is the Maya, and that is nowhere near the level of tall play of Venice. VI seems to have overall moved every civ toward having a higher city count (a change which I feel was unnecessarily limiting), and until we see some number crunching to accommodate truly tall civs (Khmer may be a start?) I see no reason to believe that Venice or Haiti can exist in VI. Much as I wish that were not the case, because as this discussion reveals, VI has been extremely restrained in its civ designs and there exists a lot of untapped design space.
I disagree with your temporal regions on the same basis: outside of the usual massive civs like Ottomans/Byzantium and Macedon/Persia, we haven't seen any geographic overlap. And if there was substantial political/cultural continuation, civs have tended to be just blobbed together (see Germany/HRE, Angevin empire (Norman England and Francia with England and France), Maurya and India, Silla and Goryeo, Qin and Yuan, etc. etc.). I think based on that trend, the Mughals would be more likely lumped in as a third Indian leader, and the USSR as a second Russian leader. I even think the trend is so strong that Kievan Rus' could end up being a Russian leader.
I think your "speculation" areas are all fairly unlikely. Much as I want Burma, I do acknowledge current political affairs might be preventing inclusion. And the rest all feel like city-states or alternate leaders. As for the "ascended" civs, we technically already have several in Scotland (the Gaels) and the Maori (New Zealand); I think this hits on several reasonable civs we could hope for: Bulgaria, Oman, Chola. I even think Switzerland is a dark horse option, even though I would prefer it remain a city-state (as should have Belgium...).