PHL-LAX-SYD using US miles
Stopover in SYD to do the SYD-AUK-CHC-AKL-SYD (paying for it)
Continue on to MEL from SYD (MEL as your final destination).
If you can do what you need to do in MEL without returning again to SYD (with another stopover) you would save yourself a paid round trip. Only one stopover allowed on the US award.
Then you could fly MEL-LAX-PHL.
Your trip would be PHL-LAX-SYD (stopover)
SYD - AUK-CHC-AKL – SYD (paid)
SYD - MEL (final destination) – MEL-LAX-PHL (return on US miles)
So in the end, it turns out to be PHL-LAX-SYD-AUK-CHC-AKL-SYD-MEL-LAX-PHL
If this makes sense to you, it would save you one paid round trip (SYD-MEL-SYD). But if you need to stop in SYD on your way home, I think you are SOL.
I’m doing PHL-LAX-SYD-CNS (final destination)
CNS-SYD (stopover) – LAX – PHL
Hope this helps. You may have additional luck on the US FT board. Many of us US frequent fliers will have much advice. I wouldn’t have been able to make my trip without the help of some of the people on the US board. If I’m incorrect in my statements above, please correct me.