While on the surface it sounds reasonable, any depth of thought will quickly reveal a few huge flaws in its use. First of all, the country getting the stuffing beat out of it would quickly be relegated to some pretty pathetic rides, that just dont fit the situation. This would tend to accelerate their losses, and very quickly make the game no fun for the losers. I very rarely fly FW aircraft because I suck in them, and dont have time to learn 10-20 planes. I fly a few regularly, and take up others when the situation calls for it, and/or just for a change.
If you want variety, all that needs to be done is provide options for each aircrafts stregths. The new terrain has made it deadly for B&Z pilots to get caught too low, because now they dont have huge streathes of relatively flat terrain. I've watched many a mustang/La7 getting nailed as they make a run for it only to realize they have to climb out of a vally...POOF goes that seperation they had.
The reason we dont see as much variety a possible is simple, there just isnt much place for 202/205 planes (for example) because their ammo is very weak compared to the other planes. I tend to see a few planes much more than others...but hey....that just means I can learn to defend against them