Just an idea, in order to get teams that better mesh provided we go the skill-based route:
Main stats could be BPR, KD, WP, and then KD ratio for long-range (snipers), midrange (DMR/nerfle), sidearm (plasma pistol, pistol, etc), close range (shorties/swords/hammers), and heavies (plasma launcher, rockets, laser, FRG) so that it'd be possible to pick a rank 4 that's good with long range, a 3 that's good with sidearms, 2 that uses close range, 1 with heavies, etc. so that you can get some extra diversity. Maybe even tally vehicle stats if we go into objective matches.