It is possible. It is in the particles. We did it in the SoA 2 mod with the Borg.
I dont think Gameplay.constants deals with faction particle usage. Sins shares many particles between all factions. Rebellion changed some of it to be more faction specific. The phase jump particles are an example. All factions shared the same effect before rebellion.
You will need to create separate explosion, hit effect, smoke, etc. etc. particles unique for the faction you intend to use them for. Have weapons, ability, and ship entitys point to these new particles.
Know this. While you have a little room to play with in Rebellion. It is possible you will 2 gig crash if you go overboard with the effects, or have too many textures.
There are tutorials on how to create particles with particle forge, and how to hook them into the game.