Topping this because I was playing with the itinerary validator (which is, IMO, a spectacular and useful device) and found a glitch.
In invalidates PER-MEL or v.v when there's a true transcon in Oz (SYD-PER etc.)
The prohibited city pairs for >1 transcon are PER-BNE/CNS/SYD, not MEL.
A small potato.