I have a certain idea. Players can spawn in a set area of the world. So lets say Server host generates a 1000km^2 map. Players will spawn at certain points on the map and they're given 3-4 minions. You can also ally with other players a sort of "alliance" where these minions will live together...
If you want to attract people the minions/citizens need personality, individual stats, and purpose. Similar to Dwarf Fortress. :)
"A very basic form of Dwarf Fortress is Gnomeria."