The sarcophagus is a bit of a dead end… there were dead soldiers down there at some point to give some sense of closure but most of the random NPC quests were designed to direct the player to explore places they would probably otherwise not bother with (prison, cough cough). I had a tunnel structure that was similar to the ant colonies that spread randomly… but there wasn’t anything really worth seeing other than additional waste bunkers. You can see pictures here:
http://smf.cataclysmdda.com/index.php?topic=941.msg19880#msg19880
The only real future I could see for the basement is a sort of endless battle pit… thousands upon thousands of corpses were dumped there so fighting a never ending stream of behemoth zombie amalgamations for fun could be a thing. I guess we could also add a stairwell and hijack the triffid/fungal code to create a re-spawning zombie field where the only way to stop its spread is to detonate charges and seal the elevator/vent shaft. If the wandering zombie groups ever get fully implemented I guess the HWS could spawn one every few days or something.