I think HKG-BNE is regional, what about HKG-ADL and HKG-PER? Assuming you really want to arrive and depart on CX through SYD or MEL only, then best would be something like

SYD-ADL-PER-SYD as your 3 australian sectors with longest flight overnight on the better domestic business

or if want to include NZ SYD-AKL (on LA)-MEL-SYD with SYD-AKL being better than AKL-SYD if flying LA (both schedule timing and service).