ya, thinking about their new technological line,new building models,and new unit models In RTW,Imperial Unit were Implemented,but one must read about how the system build and changed from augustus's time to the time of Trajan,even to Serverus. I think that in imperial rome,like carthaginians can build different "Colonial buildings" and hire different auxillia unit like Germanic Auxillia Skirmisher Parthian Horse Archers North african camel light cavalry or Nigerian-skirmishers Parthian archers I believe that difference can be implenmented as building a christian church or a roman pagan building (I belive for roman pagan,Temple of jupiter or Temple of Mars will be enough) and i believe the champion unit for imperial rome can be praetorians