Changing the fuel loadout or ammo loadout, maybe, but not changing gun sets. The only time this would be worth making the game even more gamey for is when you have to rearm on a totaly trashed airfield with the numbers against you. It just gets too close to being as arcade as instant repairs. And I would like this one myself, I like flying a plane till it falls apart.
Like Rondar said though, if you want a new plane, just tower out...