Personally, if the stronghold has stores, I'd like to see each store request that the player provide them with specific items, and accept his/her request for specific ones. No need to build a mini-Recettear inside the game; simple interaction with stores that are already in place ought to suffice.
Personally, after having played Portal 2... I'm thinking that maybe, just maybe, the Endless Dungeon would be the perfect setting for a co-op multiplayer dungeon. Different experiences for single-player and multi-player... that would rock.