Challenges to Get a Skin

I feel like Riot should allow each summoner on the rift to get a skin of some sorts without finding it necessary to pay for. Thus, i have created the idea to allow each summoner after obtaining a level 5 mastery on his champion, the summoner can then complete set challenges for each champion and then getting a skin for that champion. The skin does not have to be expensive, it can be a random skin for that champ.