The Part that could Make or Break a Great game this is becoming would be Fortresses... Not Too Sure how to Make it Flow with a Fortress but, you Could Start it out as if you get to Pick your own Plot and Plots!
There would be Different Size Plots, and always the abality to Expand a Plot! You may even Make the City ab able to Share a Small Castle, by designating part of the Plot!
I know the Word Ever Expanding is an Untold Term in Coumputing Games, But there are ways around it, for One letting Players Expand there data Space in the Form of Land with Actual Money is one, but Not Desirable
The Other Way, is Available Data Space With Game Created Currency, and Setting Faction Ownership over Land!
The Key to this is the way you'd Start!! Say buying a Small Plot and Forging goods to sell at Market Places, and Consumables Your Palace Citizens Use!
In Other Words it Would Be Much Like SimCity but, The Castle Owner or Who Ever Owns Majority of the Palace, Castle, extra
Can Sell There Goods to other Players, and rent out Plots in there Castle!
Maybe Even Have Infuance over Market Places to earn More, and pay Others to Defend them in Time of Need!
Now this Is All About What Equipment you Manufacture, Equip, and The Builds your Allow to Build Pertaining to a Rich, Poor or Reguar Sector, with the rules of ones Role in your Palace!