While I agree that the A20 is certainly tops in the "easy mode" department for dispatching gv's, it doesn't really deserve a perk. It is limited in multiple ways. The F3 mode really facilitates the easy mode. If the A20 didn't have that it would be a much different story. I actually wish HTC would change it to attack class exclusively, it isn't like we see it bombing from 12,000 ft. It is a direct support/direct attack aircraft without a doubt.
Here is why the A20 does not need a perk price:
First, take out ord bunkers = no A20. Any 4/.50 cal fighter can pull that duty off.
Second, it is a big target. Easy to hit. While in a gv just sit still get under a tree. If you're in a AA gun, sit still and WAIT until he is close enough to get solid hits. No more A20.
Third, it is slow and not the most agile especially when loaded with 8/500 lb bombs. Empty, sure it will surprise many fighters.
I'm more concerned by the tank busters armed with guns, the Mossi FB Mk VI, the 190F-8, and other gv's. The A20 is ultimately a 1 trick pony: bomb gv's. Like the Lgay7 and other such easy mode planes, I scoff at those who constantly use them and forget the challenge of using fewer bombs, more precision, and otherwise more challenging vessels. But alas....