Deathidge i think you dont know what were refering to.

Peresitant worlds is a term from Neverwinter Nights. Basically its a multiplayer server that runs indefinitly and has serverside characters.
they would usually have populations of aorund 20 people, and ofthen enforce ruels such as constant roleplaying.
the content was almost always entierly custom and ofthen reliat on a DM beeing present to spawn enemies and roleplay as the NPC.

That beeing said several servers had stuff like respawning dungeons, random NPC camps and even World bosses.
Think of it like a miniature MMORPG but with constant GM events (think Everquest 1), roleplaying and people larping as Drizzt beeing realy annoying.

From larians side this requires:
-GM mode (they already have that)
-More than 4 players allowed in a MP server
-Support for user created modules (probably have that9
-Drop in-drop out DMing
-Moderating tools for the DM/host

thats... probably it realy. I dont think you need anyhting else.