As an outside observer, I've heard good things about Jarrod Fletcher. I know he lost in a dual meet against Shawn Estrada of the USA, but Shawn has improved a lot and is a good boxer, and I think Australian Amateur boxing is disadvantage because of what I've heard are the age limits on how early you can start, etc. That and the qualifying region they advance through isn't the strongest and Australia is the best in the region, so they only get experience competing against peopkle on their level, or better, at international tournaments and duals.
Jarrod's the most solid medal chance IMO. He won the Commonwealth gold, and beat awkward pommy James Degale.