I would lightly perk 3 cannon La-7. That creates an incentive for players, it makes the game more interesting but not more frustrating, if the perk isn't very high.
For example, the famous car game for playstation, Gran Turismo: it features over a thousand cars. Would it be a better game if you were given 1000 cars to choose from the outset? No, you have to earn the better ones, that is part of the appeal of the game.
Creating a similar system for AH, with most planes having a perk cost would alienate players, I guess... But giving a better variant of an already very capable plane a small cost? The benefits outweigh the disadvantages IMHO.