New Class of SKins

I wish that all skins were earned and bought, meaning, one has to have a certain number of wins with a champion to be able to buy his/her skin, but since it is just my thought, it can be wrong. So i felt like if a person is good at a champion, a new different skin becomes available to him/her which he can then buy with RP, but it is not available to people who just bought it and cannot play this champ. This is just a thought, tell me what you guys think.