The A330-500 shrink project, to replace the A300/310, was actually several projects; first, a simple shrink of the A332 was offered - that proposal was quickly rejected by LH
as the result was a super long range aircraft and LH
was far more interested in a large capacity aircraft to fly between FRA
and MUN. Next, the A330 cockpit was merged with the A300, and of course some systems updated to the new A330 standard (there were other issues, nothing is that simple) but SQ
was totally underwhelmed by the result. A final approach was a slightly shortened A332 fuselage with a new wing (based on the older A300 design) and new engines....according to rumor, this proposal almost got off the ground but its timing was wrong as the airline industry was already suffering its major downturn and SQ
had already extended its 777 program to replace A310s.
Airbus will come up with something at some point to bridge the gap between the A321 and the A332, especially for shorter haul markets, as this segment may become important as pax numbers rise and frequency cannot be increased due to airport slot limitations. I still think that the solution will be a wide-body type......Boeing's very good and very economical 753, which should have done better in the market place and could have replaced older large airliners on shorter-haul routes, was not successful due to its single aisle, long fuselage layout....passengers (especially those in Asia) prefer high capacity aircraft to be widebody and there was much concern about the time it takes to unload/load a narrow body airliner.