They already established, in Loki, that not every person is the same sex or race throughout the multiverse.
So, wasn't there a scene at the end of one of the movies with 1000 Kangs standing around, doing nothing in particular? They should find a similar size asian guy and CGI him into that, and have him zap all the black Kangs out of existence. *poof* Kang the Assassin is born and either becomes or works for the real Kang the Conqueror.
They could also go Matrix 2/3 style and have Kang the Assimilator; where asian Kang is going around the multiverse turning all black Kangs into duplicates of the one true asian Kang.