I know it is taboo for some, but AI art might be the answer for insane volume of customization between clothes and body proportions
Until now I only heard about full AI art.
I don't know if there is some AI that manages to do a "X base, with Y colors, Z proportion of A, B clothes with each proportion, C accessories with D priority of showing, E hairs with F colors with G part showing above H part, ...".
In the end, I love AI, but I believe we are still a long way from doing this. Maybe if the game itself has an AI integrated, so any new customization comes with a new art? But I doubt that it's possible in this engine, and I'm sure that a good amount of people doesn't have a good hardware for this, and I also think we wouldn't have a good cloud thing without a expensive paid subscription.