Ok, I'm starting with the assumption that the ENY values are directly related to the perks you get by flying the airplane.
Idea #1- Change the ENY values so they reflect usage in the MA (except for the perk planes). Perk planes get a ENY of 1.0. The most used plane gets an ENY of 1.0. The second most used plane gets an ENY of 2.0. This continues until you hit the least used plane (the c202), which gets an ENY of 47 (I think there are 47 vehicles total, not counting ship gunner, plane gunner, and chutes). This would likely lead to an abundance of perk points for the good pilots, so maybe you'd have to raise the cost of perk planes some (or maybe not). These values could be changed daily, weekly, monthly, whatever.
Idea #2- Actually, nevermind, I forgot idea #2.
I think this would probably lead to some planes being flown that normally aren't. Possibly some people would get tired of flying the N1K2, SpitIX, LA7, P-51D, 109G10, and try some of the other planes out just to rack up perk points in them. I know this won't get done, but I think it is a good idea anyway.