With the caveat that I know more about insurance than I do about firearms, I'll take a shot (heh heh) at this:
I'd have no objection to drawing the line between automatic firearms and bump stocks (ban) and semi-automatic firearms (allow). As I understand it, a semi-automatic fires one bullet with each individual pull of the trigger. The "automatic" part refers solely to the automatic loading of the next bullet; to fire the gun requires a separate trigger pull. Such weapons can, IMO, be owned by civilians so long as registered and insured. Besides, semi-automatic firearms are exceedingly common. - to confiscate them all is a practical impossibility. It's far better, IMO, to require registration of current semi-automatics than to try to pry them from cold dead fingers.
I'd defer to each individual, licensed gun owner to determine whether a semi-automatic pistol or rifle is suitable for his or her needs. I shudder at rhetoric declaring that "no one needs" a semi automatic firearm. That's elitist and presumptuous and not for me to decide. I'd think a small semi-automatic pistol could be ideal for home defense. That doesn't mean I'd want one. But neither would I deny that choice to someone else who's law-abiding. Call me pro-choice!
There may be some merit in banning certain types of high capacity magazines. But an "assault rifle" is nothing more than a gun that is "military style". If my neighbor wants to look like GI Joe, that's his fetish, not mine. As long as he registers and insures the thing, then cool.
A successful insurance regime for firearms requires the law to define precisely the risks that insurance companies are to underwrite and insure. I think the best approach is require gunowners to have insurance against the medical bills of individuals who are injured by use of the insured's gun or guns. There's a parallel here to the PIP protection found in most auto insurance policies - injuries from auto accidents are covered under the owner's auto policy, not the injured person's medical insurance.. Insurance companies commonly underwrite and price such precisely-defined risks.
There are differences, of course. Auto insurance, basically speaking, insures against damage caused by the negligence of the driver. As I see it, gun insurance insures against injuries caused by the gun itself, whether wielded by the owner or someone else. That way, the owner has an incentive both to keep the gun safely stored, and to report the gun to authorities and the insurance company as stolen. As I would design the law, the owner's liability would cease with respect to use after the gun is reported stolen, thereby punishing those who don't keep close tabs on their arsenal.
The insurance regime would be coupled with registration, so a gun would at all times be linked to an individual with a legal obligation to insure. The required insurance (for victim medical bills) would not preclude a parallel scheme of civil liability for prove-able negligence. Indeed, a lack of insurance could be deemed a rebuttable presumption of negligence, thereby creating a further incentive to play by the rules.
The regulation of insurance has traditionally been the province of state rather than federal law. I'll leave for another time my thoughts on whether this tradition should be abandoned in favor of a federal insurance regime for firearms.