Nowadays even people with modern cars have them. A mate had his pickup nicked and parked up, so TBH I'm not sure there's anything you can't steal with ease.
Fit a hidden kill switch or pull the coil lead, would be less hassle. I had a clamp for my bay window camper parked on the street but never used it because it was a faff.
Fucking love that Merc. Nice one.