Like have a button in the cockpit, one that actually does something? 
I'm not too familiar with the real thing, but did airplanes have a button in the cockpit to not fire tracer rounds? I always thought tracer rounds were in the ammo belt and you had no ability to skip over them when firing the guns.
If anything, for you people that like to try to sneak up on someone and not spook them with tracers, make it like gunsights are now...each plane has its own gunsight that can be set in the hangar.