Since the only safe gun, is no gun, a ban on all civilian possession of semi-automatic weapons of any type. Waivers may be considered under certain, extremely tightly regulated circumstances.
Mental health screenings and background checks for all gun owners and possibly household members. Longer waiting periods and extensive background checks upon purchase of new guns.
A limit on the number of firearms one person can own. We can discuss what what would be a reasonable limit.
New taxes, fees, licenses on guns, ammo and accessories to pay for it.
We can discuss lengths of grace periods for turning in illegal weapons and those in excess of mandated limits as well as compliance with mental health screenings. We can also discuss nature of penalties for non-compliance and enforcement entities.