Final got my act together and my hands dirty in modding!
Just went through the VehicleSize.txt, there is a vehicle type called drones. Why doesn't it exist in any of the existing races? It looks promising as a long range cruise missile!
By the way, if I add an extra ship size and only make the graphics for one of the races, will the game crash? Will that race be the only one able to build the new size? Or will something else happen?