UA will need to establish and publish a more client friendly bumping procedure.
Yup.
And the best would be that the airlines simply don't overbook. You bought the seat, whether you ride in it or not, you pay for the seat whether you ride in it or not, and the airline does not try to sell the seat twice early in the process.
If, 5 minutes before gate closure, you're not in it, and nowhere to be found running toward it, a standby passenger, who has no guarantee of getting on that flight, might get the seat that you paid for and missed.
30 years ago, that's how we did things at the airline. When the little paper sticky tab was pulled off the seat chart for that flight, that seat was assigned to a passenger who had a boarding pass in their hand - with that sticky on it! That seat could not be resold. It was simple.