I'd like a checkbox for tracers for each set of guns (primary/secondary). Sometimes I don't want MG guns with tracers, but if I'm using a gun with bad trajectory (*cough*30mm*cough*) I'd like to see just its tracers.
Also, sometimes I'd like to set cannon to invisible and MG to tracers, for "spook" factor, to make the target turn or something.
Just a whimsical idea.