German Shepherds, huh?
Certainly far more than adequate security systems for your cars (and again, clearly a quality O.E.M. option). My Rottweiler is a tad over 80 kg on the vet scale, and he stands over 31" at the shoulder (if it's appropriate to mix standard and metric measuring systems). I wanted a big Rott, and oh mamma, I GOT one!
Still, there are downsides to having such a security system, as you've pointed out. A 175 lb security system is probabely frowned upon by those craving an optimum weight/power ratio. Another issue I face is the fact that my dog sits on the front passenger seat. My front seats have sheepskin covers, and are thus better protected from big claws and such. My biggest problem thus becomes the floor shifter. It is occasionally something of a challenge to keep my dog from changing gears without the captain's permission. He also likes to change radio stations on me.
Both of these issues could be easily overcome by having, say, a Chihuahua or Pekinese security system. But that just wouldn't be the same at all, would it?