My idea of law enforcement is to be certain that the duly-constituted police forces have superior weapons, firepower and training to overcome those citizens who are bearing arms to carry out unlawful purposes.  Making it possible for law-breakers to have full--auto weapons does not advance that goal.
If full-auto does not increase the likelihood of rapidly hitting more targets with more bullets, then why does the military use it?  
I am not concerned that your desire for legal short shotguns, silencers, and fuil-auto is going to gain any traction among thinking citizens or law enforcement professionals.  if there was that possibility, then why hasn't the NRA already jumped on it?