HKG-AKL would be on Cathay Pacific (CX), while Australia (PER,ADL,MEL,SYD,CNS,or BNE) could be on CX or QF, and the reason to go so far out of your way, other than the nice CX J service, would be to get a second carrier for your OneWorld award in the event that the LAN SYD-AKL flight isn't available on dates that work for you. Since the OW award only counts the distance between stopovers, SYD-xHKG-AKL "costs" the same mileage as SYD-AKL direct. You could even arrange an overnight in HKG if you like.

You might be able to swing your itinerary with a couple of intra-Australia awards (20/35k miles): one award MEL-PER-AYQ/ASP and a second AYQ/ASP-CNS-SYD. This would cost fewer miles than the OneWorld award, and you wouldn't need to worry about the second carrier, but you'd have less flexibility. For example, with the OW award, not only could you route via HKG, if you like, but you could add a AYQ-ASP leg for no extra charge or even go and visit DRW if you want...

Let us know what you decide to do.

Michael