I saw this review for Barrowmaze which got me thinking about the structural questions brought up at one of the Pints.
I was thinking about Left 4 Dead, which is a zombie survival game, where each level begins and ends with the players reaching a safe house, and locking the doors. I wonder about a megadungon, where the 'safehouses' in the dungeon are more distinctly indicated. While finding an empty storeroom and spiking the doors shut for the night is pretty classic, I wonder about occasional room that has a wards against evil creatures.
Also, one game I played (Diable? Dungeon Siege?) had pylons that when activated opened gates back to town. And then from town any of the activated pylons could be teleported back to. For something like Ran Lithby, it might be interesting if there was something like that, but only one 'pylon' could be active at a time. So each time PCs returned to the dungeon, they could either walk in the front door, or teleport to which ever magical access point the last party teleported out from.