I suspect that any airline operating with such reduced loads, would not have a full compliment of crew, to keep operating costs down. I can't speak for QR regulations, but there are options available when you operate with a minimum crew and then you lose a crew member.
Given the length of the flight, there would be 4 pilots, so one of the pilots could sit at a door for take off and landing (we do that at when we operate short with no replacement). Also, with no passengers, not all the doors have to be manned or armed. You probably would arm the first 2 sets of doors, with crew in jump seats at those doors and the rest in the cabin. But you can also have everyone at their jump seat as normal.