Well, if you want a zero cost idea to significantly reduce ATC delays in the Northeast then seat requirements would fit the bill. Simply put, there are too many airplanes in a given amount of airspace. The most obvious way to fix that is to reduce the amount of airplanes going into that busy airspace. If you reduce the flights it's logical to fly airplanes into that airspace that can carry large amounts of people.

You're right, Im sure there are lots of ideas that are cheaper and easier to implement. Smaller airplanes with more frequency into the busiest airspace in the world coupled with the Passenger Bill of Rights will fix everything.