I once wrote a D&D 4e adventure using a dwarf fortress as a basis. I threw it into an adventure that was more focused on some noble elves, just as a side quest, but this fortress part was for a full session.
My adventurers came to the dwarf fortress because no one had heard from it for weeks. While investigating, they found a couple of hermits and rotting corpses remaining after an apparent major tantrum spiral and other events that virtually wiped the population.
The fortress was on the seashore and guarded a man-made lagoon full of terrified, sentient captive mermaids. (One of the most striking DF stories I've ever read is the huge 40d thread about mermaid breeding...there's something deeply disturbing, yet somehow interesting, going on there.) The mermaid keeper, a hermit, was basically fine (although creepy, abusive, not very smart, and not afraid to commit acts of casual violence against mermaids). He kept doing his beekeeping and feeding his mermaids, but he didn't know why the dwarves inside the fortress had stopped bringing him more food to give them. He had orders to stay within a certain area and, being terrified of breaking rules, wasn't about to try and find out what was going on.
As the adventurers investigated, they found the fortress had been taken over by a gang of lizardmen cooperating with demons that the dwarves had apparently set loose at the bottom of the fortress. A couple dwarves had been enslaved instead of killed in the attack/tantrum spiral, and were being forced by the demons to fight each other in their own arena.
There were gruesome scenes all over the place--I tried to stick true to DF. There was also a lot of treasure--too much for the adventurers to plunder. I had to go easier on the traps than I would in real DF--otherwise I'd have dead adventurers.
I'd like to DM more settings like that one. DF fits really well to D&D. You can do so much with levers and traps, statue gardens, enslaved sentient creatures, arenas, ponds, reservoirs, engravings, different light levels, treasure rooms, mazes, insane dwarves, animals and enemies of any sort...all kinds of things really. I sure couldn't fit every idea I liked into one session.
Unfortunately I'm more of a storyteller than a builder. The pen-and-paper system helped me there, because I could draw pretty general pictures of traps and rooms and just add detail if it became necessary. So, I guess this probably isn't incredibly helpful since specifics would be needed for computerizing a system--but I thought I'd post anyway since (I love DF-themed D&D! and) the ideas might help.