"new requirements"
Something the FAA does when the occasion arises, as with new requirements for FBW helos. I wonder if the burgeoning market for air travel, clogged airways, real estate available for airports, will see a movement towards larger aircraft.
engines are high-up
Return of the 1011 & DC-10. No problems with routing fuel, all three engine jets managed, and most, if not all jets, have pax sitting on top of fuel tanks - centre wing box and maybe tanks in the hold.