There is an advantage of the rap back system that does make sense though. Say you commit a serious crime and are convicted in another state but you already have a gun registered in Hawaii. There is a good chance that Hawaii will never learn o the conviction in the other state and a gun may not be taken away that should be taken away. With this new system it will notify Hawaii that the individual had the conviction so it will close gaps that people slip though. From an efficient law enforcement standpoint it makes good sense. But it does still carry all the risks of a firearm registry.
That is why I seriously hope that in a Red Dawn type scenario, someone has the wherewithal to go and delete the registry.
You seem to like "what if" scenarios so here's one.
What if you own guns in Hawaii. You travel to Maine to go camping and hunting. Maine has relaxed gun laws, so you take a nice .44 revolver as your sling pistol along with a couple of different caliber hunting rifles.
On that same trip, you planned to visit family in Maryland. As you're driving south, your rental car has problems. It's late, and the rental car company says you have to wait until morning to get another car.
The car just happened to break down in New York. NY is nowhere near as gun friendly as Maine! While helping with your luggage, the hotel bellman notices the gun cases and other signs you are traveling with hunting gear. He also knows you showed a Hawaii driver license at checkin.
An hour later you answer a knock at the door. No, it's not the rental car company showing up earlier than expected. It's the local police. The bellman reported your guns and now you are being subjected to a search.
You have now been arrested for having unregistered firearms in NY without permits. Had you not stopped in the state, you'd be fine. Now, your life will be changed for the worse.
The RAP-BACK system doesn't need a conviction. "Innocent until proven guilty" doesn't benefit "safety". You will be added to the system just for having a "run-in" with the law.
So, while you are spending all your vacation money and life savings to fight the New York gun charges, you will also have HPD showing up at home to remove all of your guns there, too! They won't need to wait for the New York case to settle. They can use the RAP-BACK report as evidence you broke a law in New York.
So, yeah, this is a great idea! Continuous background checks that report you at the beginning of your encounter with law enforcement rather than waiting for a conviction that should be entered into NICS.