What I noticed on Roma Surrectum II with their economy was, that it developed very differently with big and little factions. Whenever I picked one of the big factions (e.g. the Seleucid Empire), but also Parthia, for some reason, in the long run it was impossible to increase the income to a point where I could build buildings in every city every turn- in every city, where construction wasn't already underway, obviously. Whatever I did, it would only rise a little bit and growing squalor and unrest forced me to let my own towns rebel and exterminate them sometimes, like it happened on vanilla Rome.
Now if I played a little faction, I would also get a good income at the start (not the last because of the treasury in your capital) and after only 20 turns in I had stored enough money for basically the rest of the game. Similarly, public order was easier to control since your starting towns were always content and you yould decide over the fate of the newly conquered ones.
I liked the system of RTR VII somewhat more. With choosing how to occupy your town by implementing a certain policy (shown as a building that was finished after 0 turns and didn't cost anything) and then developing different ways you could keep the public order stable. Similarly in your economy you had to choose a certain chain of buildings (similar to Rome II or Shogun II) and that restricted the number of buildings with income. The only minor weakness would be that controlling public order was too easy sometimes- and I didn't really understand why the town always rebelled when a new building was finished (sure, a new policy has to be accepted by the people at first, but it was really annoying, especially because it could kill your general which isn't too realistic). So maybe we could combine the advantages of both (if it is technically possible) which would make both the economy and the public order difficult enough, but also keep out random elements you couldn't control at all like the increasing squalor- which, for me, was one of the biggest flaws of vanilla RTW.