A ladder, with points assigned formulaically based on how close the teams were.
Something like 50 * n * 2^((R1 - R2)/300) where n is the number of players, R1 your teams rating, R2 the opposing team's rating.
In this system a rating gap of 300 points causes double/half points to be available depending on which team you're on, thereby encouraging but not forcing closer match ups.
Also more points are up for grabs in bigger team games, so while 1v1 are not excluded rewards are greater if you can get more clan members online.
For 1v1 this looks like:
- graph.png (11.17 KiB) Viewed 1314 times
with the x axis the rating difference (when you have less rating, you earn more) and the y axis the points earned.
Individual clan members could also have their total points haul tracked, this allows lower rated clan members equal opportunity to shine.