You could go HKG-AKL on CX and then back to Aust to get a few more miles. From CGM.
HKG-MEL-AKL-BNE-CNS-SYD 9745 miles or
HKG-AKL-MEL-CNS-BNE-SYD 10092 miles or
HKG-AKL-MEL-BNE-CNS-SYD 10272 miles

You could go to Alice Springs or Darwin that are interesting place's compared to big cities

Some on the Aust-NZ QF flights use B737's or B767’s with domestic business class seats. Some segments, like QF25 MEL-AKL, use B747 with international configuration business class. Pick your segment-aircraft if that is important to you.

Also need to consider the time of departure & arrivals and if want to maximise or minimise day or night flights.