I'd love more customizations for existing races. Elezen really need some face options that are less... niche. Miqo'te need more options for everything, if only to make the legions of catgirls less same-y. Pretty much everyone wants to mix and match Au Ra horns and faces. Or how about having different kinds of body types, so characters could be skinnier/stockier in addition to having adjustable height? Lots of stuff they could do to add variety.