Kharma is great for knowing if maybe someone will quit, but doesn't tell you how experienced a player is/might be. Perhaps a system where everyone starts at Rank 1, then after they've won 5-10 games against similarly (or higher) ranked players they are bumped to Rank 2, and so on.
2nd place gets you nothing, bots in the game make it not count, winning against lower ranked players doesn't count. Drawbacks: not sure how to prevent a group of friends from gaming it through a bunch of games to increase their ranks (which people will do, even though it's pointless in a way).
I'm not really looking to rank people per say, just play against similarly experienced players. Create some way to know you are playing experienced or inexperienced players. Create some way for inexperienced players to have fun games (not win at all cost jerks in the game), and competitive players to play challenging games.