As long as AA uses a very small memory footprint (and not too much data), spinning up new servers from a larger server application could do some awesome stuff. (not unlike instance dungeons in larger MMOs) So, lets say that it's modded to spawn up a server for "e1m1" when the quest is started. And that server stays open until a player exits... so any player is able to join the map in progress.
This should be a simple change (barring the way scripting works for spawning scripts and cross client sector changes, which has to be queued and ran instantly for new players) and would be very close to a persistent world.