Mastery Tiers 8-10

Riot's mastery point setup is a decently cool mechanic, and although i wish all the mastery points gave you more, I'd like to instead talk about the possibility of tiers 8-10.

Tiers 8 and 9 just being a continuation of 7 (T8 needs 4 s rank games, T9 needs 5 s rank games)

But for the sake of the argument, why not make T10 special? As an example, you can only have 5 tier 10 mastery champs (your main 5 champions), you unlock tier 10 by buying a T10 coin (in loot for IP) and upgrading it by having the required mastery points with that champion (as an example, say 5 million mastery points + the coin = lv 10 champion mastery), and that unlocking a T10 mastery actually does something for your account.

Thoughts?