Living in NZ, I wouldn't waste my DONE on flights in Aus, see some of the rest of the world, rather than parts of AUS that you can see at any time.
If I was doing it I would do something like
WLG-SYD-JFK-MIA-LAS-DFW-ANC-ORD-BOS-SFO-LHR-DXB-LHR-IST-LHR-HKG-SIN-HKG-NRT-MEL-WLG
This might not be completly correct because the MIA-LAS flight might be classed as trans-continental and you can only do the DFW-ANC in the summer.
To maximise your points fly syd-jfk (single flight number) and also fly europe to the west coast of the USA.
I just did the following and got 2010SC
ADL-BNE-AKL-HKG-NRT-HKG-SIN-HKG-LHR-DXB-LHR-SFO-BOS-SJU-DFW-ANC-DFW-JFK-SYD-PER-ADL
I did this as part of a business trip and the flights within Aus were for business only.