Peng Qi
Emperor
The Tatars had a proper civilization in the Siberia area, as did the Khanate of Sibir (Sibir=Siberia).Yukon, Sibera and Australia have no civilisation history before the European colonisation; no, Inuits and Aborigins definitely are not civilizations but hunter - gatherer nations. The only nations we can put here are Canada and Australia, but I seriously doubt they are first priority civs - of course looking from game perspective and lot of other historical not Eurocentric candidates.
Speaking about Carribean, I don't know about any historical empires uniting this region and I'm skeptical about one - really - small - island - civilisations
Central Africa in terms of empires has mainly Kongolese states, Kilwa, Kanem - Bornu and in far south - Great Zimbabwe, which in my opinion should be in this series instead of Zulu empire size of Belgium and life span of few decades
Central Asia has damn lot of powerful steppe empires.
I feel about the same way you do about the Caribbean (and Yukon and Australia). I don't think anyone significant enough has ever laid claim to it who isn't already in the game under a different name.
Central Asia does have a lot of candidates. I'm surprised they didn't use any.