Instead of making the high end planes harder to get, make the low end planes more appealing. Incentives work better than punishment.
This can be done easily, just by enlarging the ENY scale from 40 to 60, or even 80. The perks earned by killing one good plane and dying in a 60 ENY plane should far exceed landing two kills in a 5 ENY plane. That is how you get people to fly different planes. Everyone can still fly their favorite crutch rides, but if they want to fly perk planes, the quickest route would be to first put themselves in danger. Risk and reward.
Eliminate the perk bonus for landing. Landing safely is reward enough, especially with kills and/or damage. Running away to safety is not something that should be encouraged.
Eliminate spawn points to the strats. There is not enough players to babysit them, especially when you up to defend and the enemy bails or towers when he sees a darbar.
Eliminate town resupply. This is really a lame, non-combat way to defend and only encourages bigger hordes.
GV darbar. It is easy to determine if the enemy air force is large or small but impossible with ground vehicles.