Flat chest options for fem models, so much, omg! For that matter, non-flat chest options for masc models. Pronoun selection. Fangs for all! I'd love being able to have horns + wings always, and for horns to not be a hat slot so hats can still be worn with them. Multiple makeup options would be amazing. Piercings + tattoos! Eye glow for all would be super cool too! I really love your suggestions, OP.

Not quite character customization, but relatedly: removing gendered clothing and making it just two different clothing models that can be toggled. And I'd love to remove the race restrictions too, some of the shirts/starter gear is so amazing and it's sad if your character can't wear it.