In my view you don’t need to get crazy about the switch. You are only trying to discourage someone until the battery runs down from the starter. I just used a plain old rocker switch for $5 and mounted it in the change pocket in the dash. You couldn’t see it and was convenient to flip to start the car every time. Make it too hard and you won’t use it.
If you have an electrical pump, and you probably do, have your mechanic run a switch to the circuit for the pump, then to the inside of your lockable glove box (make a shroud housing for it so your gloves won’t accidentally knock it shut). You can also do this with other essential items if the pump is not available. If your car is under warranty, I’d ask a dealer to do it.
When I used to do this, electrical systems were far less complex so I don’t know if this would work now.
I often had a fuel pump cutoff switch in my cars until I found the Ultimate Theft Preventer – driving decent enough cars, but ones few people want to steal. IMHO life is too short to buy too expensive cars that you always worry about.