I think it would be interesting(even though it's probably not feasible), that since as we know the Roman economy boomed during war time, whereas outside of war time they racked up serious debt problems and slower economy. What if maybe based on soldier count the Roman eco benefits when there are more quantity of soldiers giving certain bonuses when above 60% compared to total population ratio of men to women and remains stable when its under say 60% compared to total population ratio of men to women. Then suffers when the percentage falls below a certain number (say 25%) compared to total population ratio of men to women. With maybe a 5 second reduction on tech research if the bonus is in effect, and maybe a couple seconds off of batch training time.
It also brings up the thought of a timer of last battle or fighting activity that helps that bonus.
As I said this timer idea doesn't seem too feasible in case of multiplayer especially, where unless you suicide a soldier or use rush strategy it doesn't really add to the gameplay, more to depth.
Just a thought towards the differentiation wouldn't mind hearing what y'all think of eco bonuses to Rome and civs in general in "wartime".