Thanks for the suggestions! Ramblings and brainstorming like yours has helped and been implemented before, and I really like hearing peoples ideas! The vending machine and deployable box was new and interesting, gettin' the gears in my head crankin'. :)
About making noise, you can walk into almost any of the objects to make a sound that guards react to. They'll look a random direction and then turn 180 to continue patrolling, so it's possible to steer them a little bit.