There was a Rome mod for M1:TW, but I haven't played it. M1:TW has a better tactical A.I. and better battle maps (they aren't dominated by a single feature like in R:TW), and I think the combat engine is more balanced, so if you do not mind the dated graphics the battles are a major improvement. The campaign game has its pros and cons compared to R:TW. The strategic A.I. isn't better, but the risk-style map limits the scope for stupid moves. The A.I. always has a clear idea of how powerful you are, and is therefore less inclined to start stupid wars (although it does seem to think that attacking your fleets is not a hostile act). Diplomacy is rudimentary, and trade very difficult to conduct. The M1:TW trait engine is just poor: you cannot change the traits, only rename them; and once gained a trait can only grow stronger, not weaker. There are other unmoddable bits as well.

So, overall I think that an EB for M1:TW would produce better if uglier battles, but the campaign game would be more challenging in both good and bad ways.