Hi Cabinmaster, a lot is left out. It's more about the general idea, concept.
I think the 200-250 seat segment isn't that small. If we add up all the 757s, 762s, A300s, A310s, Tu154s and a lot of twin aisles that are (mis) used in the segment I think it's a reasonable market.
Yesterday I cut and pasted a more radical re-engining of the 737, in case Boeing thinks a limited "plus" won't pull them into the 2020s.
The cockpit should also be considerable less noisy.