AKL-KIX(stopover)-VIE-LHR-MAN-IAD-NYC-YYZ-NRT-HKG-SIN-AKL
I don't really have a comment on the routing, more on the stopovers.
Which airlines are you planning to use for MAN-IAD-NYC?
Would it not be better to fly from LHR to IAD? Does BD offer a flight from MAN to IAD?