I don't want to be too serious on what is a lighthearted thread, but I'm amazed how often these "bring back the x" ideas pop up. Often
the 757.
Manufacturers fight for and argue over 1% fuel burn or 100kg empty weight. Proposing something that burns 5% more is like giving the
competition the keys to the safe. In fact the idea would be canned before the brochure is dry, and the marketing team sent to the gulag
for reeducation.
Certification? Well you could always try the FAA, they seem to be a soft touch.