I know that Pyro mentioned a few years ago about adding a perked ordnance system to the game, I would also like to see other options be included as well, such as having ram jets for the P-51D.
Here is a P-51D outfitted with ram jets.

Here is another P-51D with ram jets at the wing tips.

While already among the fastest planes in AH, I feel that there are too many planes that can still catch the Mustang. Having the options to spend perks to outfit the Mustang with ram jets will place the Mustang at the top of the fastest fighters in game, one that could even catch the speedy Mosquito without any troubles.
ack-ack