IMO the only un-perked plane that should deserve a perk status would be the LA-7 with 3 guns.
Its should have 2-guns un-perked, a great majority of them used in WW2 ETO had 2 guns only.
Its like some have asked in wishlist to equip the A20 with Hispano's. Noone would fly anything else but the Hispano version, much like the 3-gun LA-7.
It catches most planes up to 10k, have acceleration like few other, dive up to 550mph, turn ok but not good, have 50% more power than the 2-gun version of LA-7, can carry bombs.
Only a few other unperked planes have same k/d and have a high usage (very understandably), only P51d are higher this TOD.
Range is the only snag I can find on it. If more experienced players flew it in MA it would already be perked.