Lock Picks
I think custom lockpicks (earned through picking doors, entering correct keypad codes, etc) could be great add-on. Different gem instilled keys earned at milestones like, 50, 100, 200, 500 and 1000 doors picked. (silver, gold, diamond, etc). You could also limit certain doors to once per match so you'd have to try new routes each time. Of course different colored keys and types could be added as well.