[Idea] Earn an exclusive skin when unlocking the max mastery level on a champion!

I was thinking the other day and I thought why not have an exclusive skin for each champion that can only be earned when reaching the max mastery level? If you think about it, this is brilliant! A skin that can only be earned by mastering a champion. Once you've reached the max level for a champion, you will unlock a skin that can't be bought with RP. This skin will show your hard work and dedication to the champion(s) you love. I would be willing to wait for them and who knows maybe they are doing them now? I'm sure Rito has thought of this idea before.

What do you guys think? Good idea or Meh?

EDIT: I understand that making skins are not easy to do and could take months to make. But with Riot's resources it's diffidently possible. It would take a year or so to complete all of the mastery skins but I think it's worth it. I mean look at all the skins riot has now. There's probably close to 1000 skins by now. Making 100+ Skins for Mastery Levels shouldn't be impossible for Riot.