Vc10Tail
Airbus considered an A330 version shorter than the -200 but rejected it on economic grounds.
A 220-seat single-aisle is so much more efficient than a 220-seat widebody that there's really no contest.
As long as you don't mess with the single-aisle by adding new wings, centre wing box, main landing gear and engines etc. And more cost.
I think the 787-8 is the smallest widebody we'll see from now on.
I think the A330 and 767 fuselages could provide a bases for a shorter range aircraft.
Both were even born like that (767-200, A300). For the A330 to become efficient, Airbus would have to get rid of the massive A330/A340 center wing box to create an efficient platform.
A much lighter/ composite and similar optimized wing could make a difference.
The rest of the aircraft could remain A330. But it would be ICAO gate cat D capable like the 737, 767 and A300/A310, and unlike A330 and 787.
The OEW / installed power / payload-range / fuel consumption would all be down significantly.
It would however be a major investment compared to rewinging the A320 series. But if you don't you end up with a 787-3; Short ranged, but still as heavy and expensive as a long haul 787-8.
Toffeez Re: 787-8 remaining the smallest widebody we'll see from now on, I think Boeing was studying a NSA design until the MAX, and probably still, that could be considered a WB, a 2-3-2.
Shorter boarding times etc were mentioned. How much those minutes really bring in cash wise, remains a question for me..
For the A320 series Airbus advertises the option to go for 17 inch narrow seats like the 737 to make the aisle wider/faster.