If you already have this done then ignore this but
Wouldn't it be cool if there was a main hub "town map" and the town leads to other levels that serve as "quests" kinda like a real RPG like the FF games except in FPS format?
Or make a huge gigantic map where each grid of the map is a level so when you exit the grid, the map loads. Basically make the map as large as possible and when you exit the map borders, you go to the next level. I don't know if hexen can do that and I don't know if you can make a wall that shows what is ahead of you. Ya, one huge gigantic map that represents a world map and portals that take you to diffferent worlds etc.