I'm not sure if this has been up already, because i havent read all the replies, but what about this....
say the MA is like the following:-
Rooks 200 players
Knits 150 players
Bish 100 players
Rooks could have the top 4 aircraft, or top ENY valued planes (say nik, 51D, spit, La7 for arguments sake) perked to 4 perks each + perk planes at an increased cost; like it is currently.
Knits could have the above aircraft perked to 2 perks each.
Bish have top 4 aircraft for free, and reduced perk plane cost.
While the perk value will not stop people from flying due to cost of aircraft, its more of an incentive to even the numbers and it would not cause such a massive increase on the whine-o-meter like limiting people from upping would do.