Not in response to any particular comment, but what about the idea of appearance tying into gameplay experience?
One of the games I’m sketching out right now has the following situation:
-It’s set in a fictional country that is predominantly inhabited by people of two different cultures/ethnicities/nations, and this is very plot relevant
-The PC can identify themself as resembling their mother (ethnicity #1) or not (ethnicity #2 and others, implying PC is mixed race/adopted/both)
-This will add flavor text/change some interactions but will not change stats or have overtly positive or negative effects
The tricky part here is that I was thinking of setting appearance traits associated with the different ethnicities (Light/medium/dark hair, eyes, skin, etc) so that it can be part of the flavor text for the PC and be used in descriptors for NPCs, but I feel like that might be annoying for some players.