Rest assured you are speaking to a man who despises the Mos Eisley Cantina effect...good luck with your campaign flavours.Thanks for taking the time to share your ideas. Truthfully, I haven't quite decided exactly how much magic/science to include - I'm just mixing-and-matching ideas as they pop up until I find a combination that kinda fits.
I do like your ideas about reskinning humans by using the race mechanics as backgrounds. This somewhat resembles the rules in a link posted earlier and seems to be the simplest way to limit the Mos Eisley Cantina-effect without losing the variety of built-in race differentiating mechanisms.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.