One thing that would have to happen is to shut down the engines so people could safely move from one place to another on the tarmac. I don’t know how long the APU would hold out for once the engines are off.
This thread seems to be studiously ignoring the elephant in the airport. Namely WHY are there so many long delays, and many more that are much shorter but still a significant inconvenience and totally unnecessary?
As with most problems, this one is caused by government. The Department of Transportation publishes official reports of “on time departure” rates for the various airlines, and “departure” is defined as pulling away from the gate within 15 minutes of scheduled departure time. The airlines then use these official figures in their advertising. Those passengers imprisoned on the tarmac for several hours are nearly always on flights which had “on time departures”. If the plane goes back to the gate, it no longer counts as an “on time departure”. If it sits on the tarmac for 12 hours, it’s still an “on time departure”.
Only one simple change is needed, but government is notoriously poor at making simple changes that are needed. Report “on time ARRIVALS”, not departures.
And if I have to take the metal ladder off the plane down to the tarmac and walk 400 yards to the terminal, fine. I'd rather do that than sit for hours.