?!?!?!?!?!
Are you saying that Roman numerals are better for counting than Arabic numerals? I suppose you don't mean count (I, II, III, IIII, V...), but show the number of men in the army. I don't see any advantage in using Roman numerals.
Lets say we divide infantry in XXX maniples of CXX men each, supposing they are complete and you haven't lost people yet in battle. How is that better than 30 maniples of 120 men?