Isn't the damage type simply impact? I'm not sure between graph_type and sfx_index; there are other weapons also using sfx_index=2, not just the alien gun.

Edit:
Also noticed how modules extend each other in \Data\XMLSchema\AllModules.xsd. You know how some modules e.g. mothership engines have 2 functions (top speed, maneuverability) while other mothership engines have only 1? It may be possible to make other combos, like speed + maneuverability for fighters, or radar + cloaking.

I'm not really sure how cloaking works, does it lowering enemies' radar range? But if they have radar, then how?