What lesser-known/obscure civilizations can be included in Civ7?

[Siptah]

Yes, some reconstruction would be necessary...

Ah, not even that. I don't think there is much reconstruction necessary to get to a possible version of how it may have looked. It's a small rock temple with two small open sky chambers with beautiful ornamentation carved into the walls, and two not-too-large buildings (a gate and an altar) in front. But that's part of the problem, why I think a version in civ 7 would look very far from that - it would probably be embellished beyond my imagination. Either a huge valley instead of the chambers, with sky-high carved statues, and high up a mountain. Or a huge gate and altar in front of a tall rocky mountain... and of course, with lots of tents around it...

 

[Oberst Kraft]

The Balts (Old Prussians, Latvians, Lithuanians etc.)

 

[Patine]

I'd like to reiterate the Aboriginal Taiwanese (such as the Kingdom of Middag) and some form and portrayal of Micronesians.