By the way, I had time to try this (didn't get a disconnect switch, just unplugged the 12V battery). The result is that the car does not shut off. The car gets its 12V source from the high voltage battery when the 12v is disconnected.
To actually do this means that the high voltage would need to be disconnected and it also means that the car cannot be locked, since the HV disconnect is in the back seat.
