IMO:
1. Rank: be in top #A.
2. Activity : not less than B played games.
3. No Noobbashness: not less than C played games vs D% of top #E players.
Explanation:
1. Clear.
2. Clear.
3. To prevent noob bashing only non-avoiders should go to playoffs. So if #top8 player will bash only noobs he won't get to playoffs. There should be player stats whether he played required games with current top20 or not.
Example:
A=16,B=50,C=4,D=50, E=20
So:
1. Rank: be in top #16
2. Activity : not less than 50 games.
3. No Noobbashness: not less than 4 games vs half of top #20