Agree -- if they were uber planes, their all arena KPD ratio would be very high. In point of fact, the higher KPD's are among the tougher planes.
And that's because the tougher planes are flown by tougher pilots.
If you're tired of seeing the big 5, I can understand that -- there are a lot of them. However, perking, blasting the factories, or whatever would be counterporductive for AH -- because the less capable subscribers would get uniformly toasted in the tougher planes, if they have trouble with the "easy" ones!!
So, limiting the "easy" planes will drive less capable people away from the game. The vets might like having fewer ponies in the air, but without the dweebs and the journeymen AH could not be financially sound -- and would likely go the way of AW.
So do you really want to limit their fun, and drive away the guys who help pay your frieght?