Skin rewards for higher masteries?

I believe there should be skins for all champs, and 1 which cannot be purchased, rerolled, or unboxed. This would instead be obtained through the mastery system. Currently, Mastery 6 and 7 do not give rewards other than a flashy icon above your head, however if we got skins then upgrading tokens would be worth it. Most people use the Mastery Flash for bm, if there were skins and icons, the amount of bm will probably drop because why flash the icon when you are already showing off? I think this idea might be hard to pull off, but the game lacks rewards for players which are not high elo, or cannot afford to buy riot points to get the cosmetics they want.