Riot, Add more mastery ranks, tie it in with the mission system.

Riot, the community is very vocal about the direction you're taking missions.

You should take the opportunity, while the system is still in its infancy, to implement a champion specific based achievement/mission system. This would be a role-static (non changing) list of achievements, that could range from "Get a pentakill with vayne" to "Reach 20k healing in one match with Soraka." And give mastery points or tokens as a reward. This would only improve the depth of the game, would take minimal coding to implement, and further increase the playerbases interest in the mastery system.

Of course there would be minor adjustments to how the current mastery system works, but thats just tweaking some numbers to allow for mastery 8,9,10.

On top of that, an achievement system would be incredible to have in the game. Everyone would have the easy achievements, "Get a triple kill" but imagine the possibilities. "Get a penta kill with no allied champions around" and offering perhaps a range of summoner icons, that you could hover over and see the person (on your team) highest achievement with that champion.

I feel you're missing a huge mark with the mission system, especially by making it revolve around special events, skins, and champions. It looks more like a moneygrab system than a mission.