When making a ship style- you should only be focusing on the hull designs, not any functional components (ie engines). This is of particular importance in TA where the tech trees can be radically different, thus even if you had say the Drengin set up to use your custom designs, if they had technology on them that was incompatible- they would not be able to use it.
anyhow, the TL/DR version: just make all your hulls/designs. leave the functional part for in game.
