Which of these are stopovers? You're only allowed 2 in the continent of origin - are the stopovers CNS and BNE? If so, why fly into MEL? Returning to the point of origin (SYD) is permitted and does not end the itinerary.
I presume for the extra points and SCs. Both SYD-CNS and MEL-CNS are zone 3 for QFF earning (and BNE-CNS is not). MEL is easier to transfer than SYD, so it makes sense to me.