top bomber pilot can fly 29s without perk loss (if they want to)
Only if you limit yourself to bombing town centers. If you want to hit anything of value you expose yourself to risk. Even Lusche loses bombers, as he recently noted only the Mosquito Mk XVI was self sustaining for him. He lost perks on the B-29s and Ar234s.
How about giving the lowest ranked pilot free perk planes instead?
Give the top ranked pilot mandatory 40 ENY equipment for the subsequent tour.
Also not a good idea. It is easy to game score to look like a bad.