BJDs! * v* Here's a bump from a fellow doll lover.
Perhaps you could incorporate other doll aspects? Like "broken" or "melted" parts could be defects. Rare traits could maybe be purer forms of materials, like resin which is real world expensive usually, and cloth being the lowest (could have see joints).
Are the hats part of their heads and the ways of having different animal ears? Or none and then it's just a beanie like?