Would it be possible to take a look at the unit upkeep values beacuse at the moment it seems as if they are too high IMO. A good example would be the parthian horse archers, as the parthians are semi nomadic the cost of upkeep should be a lot less as all the warriors already have horses and basic weapons as part of their way of life so it would not be neccesary for the state to pay for their upkeep, in contrast the roman legionary infantry would be quite expensive to maintain as all their equipment/ lodgings/ food are paid for by the state.