I found this ATM10 server called Iperios and it is all about building nations. Players can make their own nation and pick how it is run. You can set up your own government and your own laws and your own ranks.
If you do not want to start from nothing you can just join a nation that already exists. Staff help new players when they join and they give a beginner kit so you are not stuck at the start. The server uses the All the Mods 10 modpack version 5.4 so you need that installed to play.
The server is whitelist so you have to join first and get accepted. After that staff guide you and explain how things work. The whole place feels like it is built around roleplay with rules and nations instead of just random chaos.
