The Ocon vs Verstappen incident has been fascinating for me to watch people argue over.
How about this idea (I expect to be eviscerated for this, but here goes):
Rule: Once a backmarker has been passed by the top three cars in the race and they do not un-lap within 1 lap they are required to withdraw and park the car.
What this does is legitimatize a backmarker fighting for position, they have a right to not be forced out of the race. A leader has to treat their pass of a backmarker the same as trying to gain from P2 to P1, respecting the same allowance of space that would happen in that situation.
I see a few clear benefits for racing on this:
1) The backmarkers slowly will be cleared from the field, making a less congested track.
2) The clearing the field will mostly benefit P4 and lower cars, which means they can challenge higher up more effectively, possibly better overall racing.
3) Lower level teams will put fewer miles on their engines and chassis, meaning they can suffer fewer grid penalties and have fresher engines and drive trains, making for a more competitive field in future races.