I read the whole thing and it was really good. The mission/space thing (basically, create the points of interest and then map them to rooms) seems to lend itself really well to Zelda dungeons. In fact I have seen that process reversed just to talk about the dungeons that already exist.
There are a bunch of things I think you would have to do to make an actual game out of it. More rooms (possibly randomly generated to a degree themselves), the ability to swap out the dungeon item and other polish things. The interesting one would be messing with the mission to space mapping.
For instance, could you make the multi-part lock happen in a big central room that you see before hunting down enemies to open it? Could you put the items in a loop that quickly takes you back to an area you have been to before? How about short-cuts that make traversing the first part of the dungeon easier once you have the item?
You probably can, but I wonder if there is a somewhat elegant solution to it all. I am very impressed with the current system.
