Some states already have laws like this in place, but it can only come from a doctor or psychologist, not family. And even then the system has been problematic at best with the wrong people having their firearms taken, or petitioning to get them back and finding put the police already destroyed them or refuse to give them back. Honeslty, it's something that should exist but with the problems that have already been seen it certainly needs some work.
Also, that 'stored elsewhere' provision will bite them in the ass hard when they accidently violate the wrong persons 2nd amendment rights.
Many, many, many states prevent people with violent felonies from owning firearms.