Less stompy 1-sided ARAM games

The idea:

1. Divide champions in groups by champion power (only needs to be done once) (could be done automatically, sorting them by their current ARAM winrate)
2. When a match is found, the system checks which groups are eligible (= the players have enough champions from each group)
3. The system then randomly chooses one of the eligible groups (if there is no eligible group, it may join the two/three/etc consecutive groups that come closest to being eligible, eventually -if no other option is found- including every champ and becoming essentially what the current system is)
4. The system then assigns each player one random champion from the chosen group (maybe starting from the players with fewer champs in the group, to ensure that everyone gets one)

For when the meta shifts or a new patch is out: champions can move into the next lower/higher group if their winrate drops or rises excessively from that of the other champs in the group (which should stabilize closer to 50% over time after this champ's de/promotion)

Thoughts? (Please refrain from posting things like "just unlock every champ"; we already know that RIOT is never going to do that)