So called straw or straw man buyers (A person who knowingly and willfully purchases a gun for someone who legally can not own a firearm) should serve a minimum of 2 years per gun bought and sold determined by the reason the 2nd party can't buy a gun of their own.
That's already federal law. The potential sentence is up to ten years.
Does it ever get enforced? No. As such, the law has no teeth and no deterrence value.
Everything else you're suggesting only punishes the law-abiding.