Possible Mastery Rank 5+ Reward Idea?

So I was looking at my Loot page, trying to figure out what I could do. My eyes rolled across a Mastery 7 token for Brand, so I clicked it to check out what I needed to unlock it;

3 Mastery 7 Tokens and 600 blue essence 3 Mastery 7 Tokens and 1 Brand Permanent 3 Mastery 7 Tokens and 1 Brand Shard

Upon seeing those requirements, my eyes drifted over to see how many Hextech chests I had available; out of that a thought appeared...

What if I could combine a Brand shard/permanent with a chest to make a Brand specific chest, of which I could possibly get any of his skins shards out of. So I got to thinking, why not implement such a thing? We already have lunar revel crafting things, we had the Snowdown stuff as well as the project stuff. All of which had crafting components to make specialized chests with the crafting system.

Why not make something similar for champion mastery? It would give you an incentive to do well on the champion, as well as it would fill the wanted 'reward' part that everyone seems to want. Granted there are some major flaws with the idea in it's current form..

I really wanna know what everyone things on such an idea. Maybe we could improve it to the point where Riot implements it. Post suggestions and fixes in the comments if you have them!