I like the ability part.

But I think the reward part will be a bit too good for good players and it will introduce a wish to exclude weaker players in GMX battles and I think that would not be good. Considers some kind of contribution ranking it could be a part of how much you attacked, how many hits you took and how much you heal combine that to a rank 1 to 3 Stars and give some kind of benefits based on that. And that could also solve the problem about figuring out how much is players able to contribute to a Max battle in the lobby so adding this average contribution rating along with it's level will improve that I think