First let me say BigMax does an outstanding job hosting KOTH. He is fair, impartial and makes it a fun event to take part in.
I agree that bombers don't belong in KOTH. While the A-20 and Stuka are listed as attack planes, they are primarily bomber's. Maybe adding a Wild Card round once during the event would be a solution for those who like flying them. Make it known at the start that round (x) will be the Wild Card and what the plane will be.
Limiting the number of rounds would be a bad thing IMHO. If you want a shorter KOTH, learn better evasive maneuvers, use better tactics and win more rounds. If it were easy, what would be the point? Adapt, improvise and overcome. The ability to survive in the face of ever increasing odds is what makes you King Of The Hill.