Theory
Could I have one of those buttons programmed to match my key and have it work for starting/stopping the car like cars with keyless go?

Could I have one of those buttons programmed to match my key and have it work for starting/stopping the car like cars with keyless go?
I've seen it only on a W221 but I assume it is the same on the cars you mention.
I do see your point on the sensors detecting the key.
So, assuming what you say is correct, once KG has sensed there is a key in the car, the system will let the button start/stop the car. At the same time, once the system senses the key is out of the car, the system will let the user lock the car (via door handle or key fob).
Could, then, the button work on the same theory with a non KG car? Once the driver unlocks the car, the system is "good" to press the button for start/stop. And, because the button is passive, the system would let the driver lock the car without the car thinking the key is still in the ignition.
INQUIRING MINDS WANT TO KNOW!!!!

Jose
replacement part is about $20 at MB parts
but hey you can remove it every time you want to start it, just change the words, remove to insert key to start vehicle... because i know a plastic piece will do it because I seen it elsewhere.... it will be small writing
Oh well, there goes my theory of getting push button start for my ML!



