About the OD switch, I may be wrong since our autos are electronic, but I think that switch actually controls a solenoid. When you put power to it the solenoid changes the setting (OD>no OD), it doesn't matter which way you start, when you put power to it the setting changes. Therefore, I believe if you wire it "always on" eventually you'll burn the solenoid up because it will always be activated. I'd think it would be much better just to find a hidden location for a switch, and make sure you get a MOMENTARY switch.
James T