Pick rules for a race, and then just reskin it as another race.
I'm not trying to crap on the thread, but isn't this what everyone has always done? or is it just me?
The first "genasi" that I played, long before there was ever rules for such a thing, was a tiefling that had been reflavored to have an elemental parent instead of a fiendish one. (I didn't want demonic overtones for that character.) Years later, when Wizards of the Coast released the
actual Genasi, I was like....meh, no thanks, I'll keep the reskinned tiefling.
More recently, one of my players wanted to play an all-new character race of their own design, based on a Magic: the Gathering card (essentially a blend of elf and fairy traits.) So we picked the fairy race from "Wild Beyond the Witchlight," and reskinned it as an elf (medium size, humanoid, etc.)
Even back in BECM, I would reskin the Dwarves to be "gnomes," since there wasn't really much of an appreciable difference between the two...at least, not as far as the game mechanics were concerned. And I remember making a "half-angel" in BECM (there was no such thing as an aasimar back then) by letting the player roll up an Elf, but pick their spells from the Cleric list.
Or maybe I've just been doing it wrong all these
years decades.