going from what I seem to remember hearing about game design philosophy, it's better to give people things than take away, so instead of penalizing the high team more aggressively by taking away more options, just reward the low # side more..
maybe by making the perk bonus modifier more aggressive, or adding another modifier based on local population.. lower the cost of perk planes, etc. if you are earning 10x the perks you normally would, and perk planes are half price, you might not care how outnumbered you are.. on the other hand, if you're earning 1 perk for 10 kills and 262's cost 400 perks, you might reconsider your loyalty to a chesspiece icon, or decide to leave the safety of the horde and branch out.