Has Atahualpa ever led the Inca in Civ? I think he'd be an entertaining Civ6 leader, prancing about with his brother's gilt skull.
But on a more serious note, I hope we get Huayna Capac, rather than the return of Pachacuti. Gilgamesh brings us to quota on "first historical king still shrouded in legends after a list of purely mythical kings." (And in case I'm being unclear in the midst of my sarcasm, yes, I'm aware Pachacuti was a real Sapa Inca, but he's still the first historical Sapa Inca after a list of mythical kings with a host of legends attached to him. I'd much rather have the better attested [and still awesome] Huayna Capac.) I wouldn't complain about Atahualpa, though; madness can be entertaining in moderation.
Whomever they choose, though, I still insist they be as dripping in gold as Monty is quetzal feathers.