I know this can be a hot button idea to mix cosmetics with gameplay but since the skins are earnable in-game currently (not that I mind the idea of supporting the dev team further sometime). I think a cool addition to the player skins, that mostly seem to be based on characters you talk to at the saloon, would be to give them unique traits. Something that adds to roleplay and builds.
Examples being Bull can do damage/pushback when you dash into skeleys because he uses his horns. Maybe the undertaker's skin gives buffs to enemies you possess or summons like badito, making him feel like a necromancer (techromancer?).