Regularly I see fights where a group of 3 friends, often with crews in the 6-8 range, play against a team composed of level 1-3 members. Certainly experience levels don't confer additional abilities, but regardless of a general gamer's skill, I find experience levels are a reliable indicator of... experience.
I propose some metric or series of achievements that rewards players for fighting on the low-experience side of an greatly imbalanced fight (they'd have to be present both when the match starts and ends). If it were an achievement, it should involve enough matches (maybe 100+) to prolong the amount of time players would be willing to make the conscientious decision of turning a, usually guaranteed, win into a fighting chance.
I'd still favor an "honor" metric better, though -- experienced players who regularly choose the experienced side (with increased weight on captains) would have this slide towards zero (or into the negative, depending on implementation), while those who choose to even things out would rise in prestige. All of this would be relative to the amount of imbalance, with imbalance below a certain threshold having no effect (so a 8-8-6 vs an 8-8-8 match would not affect this metric for any of the captains).
To allow players to still play in clan or pre-determined team configurations without a large risk of penalty, when setting up a game, a minimum or maximum captain level could be specified to, for example, to enforce "noobs only" games or to prevent a trio of new captains from jumping into a game they couldn't reasonably win against a coordinated high level team.