I am afraid you don't understand how models work. What counts as another model is not an actual file, but rather a new entry in descr_model_battle.txt. Each entry in DMB.txt counts as one "model slot," and each entry only has one texture per faction. I could use the same .CAS for several different units, but if they must all be available to the same faction, they must all have a new entry in DMB.txt, and thus they all use a different "model."