Champion Mastery for Twisted Treeline
I think that you should be able to get champion mastery points for playing twisted treeline. Twisted Treeline might not be as big as the rift in terms of popularity, but tons of people still play it and there isn't much of a reason not to earn champion mastery points. You're still playing a champion and learning things whether its the champions abilities or mechanics.
I'm just trying to say, we need some more love for the Twisted Treeline players. Twisted Treeline is just as difficult in terms of skill as Summoner's Rift is.