Just wanted to let people know about this idea I had:
If one were to create a turret location (on a hull) that uses the feature where there is the location of the turret image (and origin of bullets/beams) and also where the turret is placed in the ship editor and also gave the turret a short range, then one could use that to create a limited firing arc. This is because the area where a turret can fire centers around the point where the turret is placed in multiplayer. This would make the turret only able to shoot a very small area. I have not yet tested this (its late), but I will tomorrow.
Sorry if this has been done before.