The only way we avoid UBC is if we make opening up NICS to the public the compromise.Wow, if true then this could escalate quickly. If he was a felon and an FFL sold him the guns, they're toast. If he was a felon and he bought them private party, UBC here we come!
Allow Joe Schmoe citizen to access NICS, run a person's info, and get the pass/fail response. Charge some nominal fee for use ($2-5).
Make it the seller's responsibility to understand who they're selling to.
We're already seeing extortion level pricing at some FFL's for doing transfers and if UBC through an FFL becomes law of the land, it'll be the government building a defacto monopoly in some locales. Expect to pay even more.