Them thar's some fine Iphone twigs in those hills and Hitech can build NYC condos from popsicle sticks...... 
There are a couple of ways to look at what we've all come up with.
For flexibility and robustness, yes, another file of parameters per plane would be the best solution from a player customizable aspect. CPU/IO overhead, however, would go up. You're now dealing with more files to open, close, build, update, .. etc. Whereas that would be nice, it would also ( I believe ) cause more programming effort.
My chart ( stack of twigs??) would be a nice compromise. By 'just' changing which gun position routine is called depending on which keystroke received ( and you're already processing keystrokes, so there should be minimal change in CPU needs ) you can achieve a large portion of the desired effect.. ASSUMING the code is structured as such, as I said, up front, and I don't expect HTC to confirm/deny how it is done.
Compared to a lot of other things going on, this probably wouldn't be a high priority.. until you're in a B29, tripping over the navigator trying to get back to tail section..