Interesting. But wow, that seems like a long way out of your way. Flying to MEL, clearing ABF, transit to the domestic terminal, and then a 2+ hour flight back up to Brissy. Not that SYD is any easier to be honest, but there are more daily flights SYD-BNE. It might be worth comparing to a connecting flight to YVR and then the nonstop YVR-BNE. At least the single terminal at YVR makes for an easier connection.
Still reinforces the point that if BNE is your final destination, a nonstop from the US would be better.
And maybe this is a good time to mention the wistful nostalgia for when CO/UA flew into CNS...