Makes me think of the old signage in windows saying the car was alarmed (when that was relatively new practice), by now having signs saying something along the lines:
"This car is protected by internal camera recording that is fed to remote recording - you have been warned!" Especially if you have the dash cams......
No doubt some will find good reasons as why that would not be sensible/useful but.......just trying to think of something to discourage these scroats that understandably makes you feel like keying them if you got hold of them! That's not the answer I know, but the law is clearly ineffective in dishing out appropraite punishment to stop/discourage this vandalism.