I like it, although it does mean producing a number of tokens that you hope look similar enough on the back that you won't be able to tell what is on the front.
I'm not sure I fully understand how you are suggesting to use them. In one part you say to use an existing quest as a template, and another that the tiles should be split by quadrant as if you are using the whole board. I also don't really see the point of moving the shadow tiles around if you are playing solo, which seems to be the main purpose - I'd feel a bit weird making things easier or more difficult for myself in the middle of the game.
You could probably expand on it a little to have a "final boss" or objective token that you can randomise among the last few rooms so that the end of the quest isn't as clear as just reaching the staircase.