Stronghold Mod
Similar towards Persistent World in Warband except you can gather Wood, Stone and Iron for building Structures, Weapons, Armor and Siege Stuff. Plus Farms and certain items like Bronze, Silver, Gold , Spice for Trade and usage.
All the Eight Factions have different types of Weapons, Buildings and troop types along with the locations having a vast quantity of a useful resource while it may have a lack of a certain resource depending on the Region.
It may hold 400 player servers or it could be commanding bots while you are lord. Of Course maps can be large so you can hide your kingdom and villages.
Might be ambitious project but I think it could be done. A Reference look at Stronghold and Stronghold Crusader.