Many years ago when a B733 was operated ex MEL-SYD-NLK I remember that the passenger load was lucky to be half or just over half full, so more than likely not profitable. This may sound harsh, but what has changed out at Norfolk Island since then that will have tourists streaming out there? Or is this just a taxi service to the mainland for the locals and if they get some tourism, then that's great.
Seeing the King Air pic got me thinking that maybe the King Air is the best aircraft for this route. Maybe a King Air 350ER 3-5 times a week for passengers and B200 freighters once or twice a week. If something larger is required, then maybe Jetgo with an Embraer 135 may be suitable.
As much as the locals may want a larger aircraft on the route, it's obvious from the airlines that have been and gone from NLK that the passenger numbers are not there. So maybe it's time that the administration out there became realistic with their plans.