Ya, that's a bad idea. I installed a kill switch. It is an actually switch but I hid it (somewhere secret). That would be your best bet most likely.
To do that is easy, basically cut a wire and install a switch. Probably going to have to extend the wires but you get the concept. Just make sure you are good at wiring. Solder and heat shrink so it doesn't come off and leaves you stuck. If you did it to your starter wire, then you could start your car at home, flip the switch, drive it somewhere, turn it off and no one will be able to start your car and they won't have seen you flip the switch.