Star Wars never wrote its own 'deep history', but thinking about the process of going from one homeworld of origin to galaxy-spanning race plus meeting aliens, means SW society is inherently diverse.If it did happen, and it was happening right now, I'd ignore any issues of gender or ethnicity, and cast the actors that I feel fit the feel and attitude and tone of each character best.
Repeated scenes where the actors are of Amerind, Aborigine, Oriental, Arabic, Western, &c origin and the characters never notice any difference between appearances nor say anything about it, would be its own powerful statement. (See also Uhura from Star Trek.)
IRL, I would prepare a one-page "press release" describing in very broad terms what likely happened, with a little bit of astronomy thrown in. When people ask "But what about...?" I refer them to the release. Repeatedly. Don't get drawn into ambushes or controversies; they never help sell tickets.
The only two characters for whom looks matter is Luke and Leia: when he eventually says to her "... and my sister has it ..." the actors had better 'look like family', not look like their forefathers spent generations on opposite ends of the galaxy - because instead of being a big reveal and deep emotional moment, the audience will break up laughing.