Sketchfab will provide much but not what you like, i.e. Your Rome. Then you would assemble different models and it takes a certain time to inject coherence into all.
Sculpting would provide you much control in that regard. Even if it seems much more work to start with.
Another option is to use an online photo to 3D model applications, but you would still need to modify the time damages with sculpting.
You could try on one model and test if it makes it faster.
I could imagine a procedural solution. But I’m not know enough how doing it, if at all feasible. Say, with addition to displacement you add some masks with ColorRamp and Mapping, then modify them for normal/roughness/color channels. If you need to make many images it means many nodes adjustments… if you could find someone who can guide you through.
Finally some historical notes:
-The Roman Empire lasts more some 500 years, i.e. more than 50 different Romes.
-Use new-classical and renovated buildings references, at least to for a realistic texture without the violence of time, ie. its effect on their stone, marble etc’.
-An element that can play to your favor… Rome was eclectic. The Romans were (as any Putinesque type leader) good thieves. While they robbed entire museums that also killed their curators so when they assembled it at Rome it looked like Putin’s American friend curated Venice bienalle.
