Quick update today on progress from yesterday evening. The new core of the quest dependency system is in place and humming along nicely, though I've got a lot of rough edges to grind down now. The most complex working piece is the "unite the pieces" quest, which now creates individual "find item" quests for the pieces; each of these creates its own location exposition sub-goal that must be satisfied (currently, by listening for rumors in town) before you can go to the area holding that piece.
The next big goal in my sights is a longer chain of quests with a few more pieces: a hostage quest with a specific goal to slay the captor, for which you'll need a special weapon that's broken into pieces that must be found and reforged. I think I can get this put together pretty quickly now, with the new works in place, but I'm starting to have to devote more attention to narrative details such as how exactly the "hook" for each goal is exposed to the player.