Agreed, a flavorful Rome would be: tall Rome & wide empire. As stated, with the current UA (-25% production of any building already in the capitol), you'll be buying the buildings in Rome that you want to cheaply produce in your empire. The more cities you have, the more this UA is a benefit. (Moreover, I think it also applies to puppets, so even a happiness hungry conquering Rome still benefits.) So, with a solid UU Legion that BUILDS roads and is available EARLY (however the resource requirements work out), then a UA or a UB (it could follow the concept of "all roads lead to Rome" with something like "Milliarium Aureum") that provides + and/or + when cities are connected to the capitol sounds much more flavorful and unique for Rome than adding (even a buffed & early) naval UU.