I have to say, the artwork on Mystic is really great and probably my favorite part of the game. On the other hand, if you have a really beat-up copy of the game, it wouldn't be such a tragedy to see it rethemed.

If you're not totally sold on using just 8-bit graphics, the artwork out of the NES/Famicom instruction booklets are pretty great, and there's some neat Zelda manga artwork out there. I did a search just in case I ever had the temptation to get a Gladiators and make it into a Zelda pinball game.

Agreed. I mean no disrespect, the dungeon idea outlined in your first post is kind of neat, but visually wouldn't make much sense to the casual viewer. Maybe each square could be a dungeon room so it's immediately recognizable as to what you're actually doing? You could still keep the weapons for the inserts.