I'm all for a undock-arming switch, or any other system that keeps you from undocking with an open airlock...happened to me once: was undocking from ISS, I had already checked that retro doors and radiator were open, and I press the big red button.
PSHHHHH was the only thing I heard, followed by a nice, big, red text spelling "You and your crew are DEAD!!!!"...
EDIT: in case I did forget...thank you very much to Doug and Coolhand and anyone who contributed to this and the other XR series vessels!