Hetairoi Kataphraktoi

I have never modded anything in rome total war and i wonder if its possible to make the baktrian late bodyguard unit,the hetairoi kataphraktoi into a normal recruitable unit?

i want to know aswell. also with the armenian, sarmatian and sabaen bodyguards. I understand that the sarmation, bactria and armenian ones are very powerful units so they should be kept as bodyguards only but the sabaen one doesnt seem that strong so i want them recruitable for my campaign (although the sabaen ones gain exp at an incredible rate)