Many people think that skins with stats can be another pay 2 win and others say is not important, buy what if we think outside of the box.
If skins would apply Elemental changes, those could bring not only new cosmetics, but also utility WITHOUT touching the stats, a Fire Elemental Bellona who could be used against wyvern and golem, a nature Karin like a "free" Baiken for those who haven't got her, or a Kayron with Dark element who does not face elemental disadvantage or advantage.
This would give a real power spike and variety to all unit, imagine you only have good water units and you have to fight against full nature teams, a Bellona with the capacity of countering this would be marvelous.
BUT! To avoid skin change abuse can be added a Change Fee, Once per week all units can change the skin, BUT if you want to change it a second, 3rd, 4tf time, you have to pay 50 SkyStones fee.