For maximum miles you can, of course add two further segments in SWP. Perhaps SYD-AKL-SYD, or maximise your CX F time by doing SYD-HKG-LHR.

I don't understand why you would do HKG-DPS-HKG as a mileage run in J when you could do HKG-NRT-HKG in F (kaiseki meal, F wines, F seat, guaranteed AVOD - DPS may have a regional J).