It's all wishful thinking.
A professional that is stealing your classic isn't going to start it. He's going to show up with a set of wheel dollies and a tow truck. Starting it is too loud, driving it brings too much attention, and there's too many variables- electric fuel pumps, cut off switches, owner altered wiring etc.
A hidden switch on the ignition side is as complex as you need to be. That'll stop your average joy rider or mouth breather. Beyond that and you're not going to stop them anyway, because they're not going to start the car. They're gonna dolly it, tow/trailer it, or in a lot of cases steal your trailer with the car inside. Your average criminal steals Honda's and Toyota's that blend in and disappear into chop shops for easy money. Not muscle cars and hot rods that draw attention and are easy to track because of their uniqueness.
