Confirmed Civs and leaders.

[Elok]

Mao and Stalin have both been awkwardly accepted and/or rehabilitated by their respective countries. Hitler, fairly or not, is still far more of an unambiguous embodiment of evil than the (roughly as murderous) Stalin.

[pchang]

I'm not sure what traits would make Hitler advantageous. As far as I know, he actually hindered German success by insisting on crappy strategies.

[Aeson]

Hitler - Charismatic and Industrious or Militaristic. Sure he applied those things to horrible and self destructive ends ... but he did inspire a people to build up a lot of infrastructure and military might.

[Aeson]

You could also make a case for Scientific.

[Ming]

Yes you could. Every great leader (good or evil) has useful traits, or they wouldn't have been a great leader

[Elok]

In Civ4, he would have been charismatic and aggressive or imperialistic. Already taken by Genghis and Cyrus IIRC.

[Lorizael]

Disagree. I'd give Hitler Protective (he just wanted Germany to have some breathing room) and Creative (he was an artist). Oops, that's Gilgamesh.

[Lorizael]

In the E3 demo video, Ed Beach says 18 civs at start, including some we've never seen before.

[Buster's Uncle]

About half the 43 are bull, IMAO, but a worthwhile read, and interesting...
43 Real-Life Female Leaders We’d Love to See Included in Civilization VI

[Dinner]

i hope the english don't end up with churchill or elizabeth I again, but i expect they will.

William the Conquerer? Edward the Longshanks?

[Buster's Uncle]

Those are strong personalities history still knows something about and would be good choices...