Champion Summoner Icons as a reward for level 6 or 7 mastery

As you might know, you will be able to purchase level 6 or 7 champion mastery with champion shards gotten in chests. However, there is really no incentive for doing so. Therefore, i have thought up an idea that will hopefully fix this issue. When you reach level 6 or 7 with a champion, give us that champions portrait used for kill display in game, as summoner icons. Due to the fact that they are already made, and made from champion splash arts, this will not require much work. I for one, would use my blitzcrank summoner icon if i got one.