Not only does this single out guns and is therefore a bad idea, such lists, in general have so many problems that the last thing we need is one more to keep track of.
My friend had two complaints sworn out on him for Domestic Violence. His wife, whom I cared for as a friend, was nuts. Her stated reason for swearing out the complaints, "I was afraid he would yell at me."
The first time the judge simply threw it out. The second time he told her that if she did such a thing again he would hold her in contempt and she would serve jail time.
Too bad he didn't just Baker Act her, because not too long after the second incident she checked into a motel, put the barrel of her pistol in her mouth and splattered her brains all over the wall and bed linens. If the judge had been a bit more alert she might be alive her kids would still have a mother!
The sad part about all of this is that, even though she was certifiable, and both complaints were thrown out, my friend is now on a national registry as having been arrested for domestic violence. He could have one such instance sealed and this might go away, but the law is clear, two times and it follows you forever regardless of the outcome of the case, even if you are proven innocent!
I can just see everyone who is arrested for successfully defending himself with a firearm and then proven innocent because it was a good shoot ending up on a list and having his rights stomped on because a bunch of bleeding hearts have convinced the legislature that such lists will do more good than harm.
I have to agree with everyone who has said, and I paraphrase, just get the creeps off the street and quite trying to fix what ain't broke!
PS Oh yeah, these registries always seem to start off as being for those convicted, and end up being registries of those arrested. Eventually someone will cry that smart lawyers are getting the criminals off of the charges so it is in the "Public Interest" to keep track of those arrested. There is no appeasing these people, give them one thing and it just gives them the energy to push for more.