You present a very good point of asking how we could make our cars less vulnerable to thieves, and this subject should be an open discussion.
Anyone with even a little "car smarts" will know it takes fuel and spark to start and run a vehicle, so there are various ways and methods to disable either function.
Most commercial anti-theft systems interrupt the starts circuit, and even the basic crook knows how to bypass that and start the car.
My thinking is to not allow fuel or spark to do their job, preferably both.
An experienced criminal could figure out how to overcome the obstacles you have done, but it may take many hours of work, and that is not what they would do.
A hidden switch or 2 or 3 would prevent most GN's from leaving their parking spot under their own power.
You can "layer" your security blanket with multiple switches and in varying places depending if you are just running in the store for a beer, or plan a long night out with your best girl!
I have one switch handy for the former, and a couple others for the latter, and of course my BEST girl is my wife!