I wonder what the ticket prices will be? One 20-hr flight uses considerably more fuel than two 10hr ones. Also, where is the demand for this over a cheaper flight that breaks the journey in two and is only a couple of hours (10%) more elapsed time in total, or gives a chance for a longer slip to acclimatise? How much payload will the aircraft actually be able to carry compared with its nominal capacity?
The longest sector I’ve ever done was just under 18hrs and I felt like crap at the end of it, and I had a bed!