Hell, as long as the guards try to incapacitate/grapple/subdue dwarves in some way before stabbing them, it would be nice, especially if tantruming dwarves have a chance to actually stop once they get whopped upside the head by a mean-looking guard.
An extra use for the Intimidater and/or Pacifier skills, perhaps, with a weapon that trains them? And I do think there should be an outside chance of inflicting lethal harm with at least some of these weapons, but it wouldn't be
that hard to come up with something relatively harmless; a stout sick wrapped in several layers of sacking, for example, or a blunted crossbow bolt with a small bag of sand or sawdust on the end.
I am kinda sad... from the title I thought this was a suggestion about making certain Stockpiles vulnerable to theft and thus giving us a reason to bulk up the security surrounding it.
I actually mention something like that a little further down, though I was thinking more about shops than stockpiles. Law enforcement definitely needs an overhaul first, though; I personally think the last thing DF needs is yet more ways to start tantrum spirals.