The article highlights a resurgence on a number of select routes between very major cities with route distances well suited. I look forward to using a sleeper on one of those routes but the sleeper in general has numerous challenges, especially for Australia.
The days of bunks are dying, the OHS laws around bunks especially the QR triple bunk on a moving train especially with a target audience of mostly older 50% of the population is a big no. This impacts heavily on cost viability. The photo in the article shows likely a design that uses a steep set of stairs, not a ladder to access a pair of bunks that are placed in the normally curved roof space, if true, this is well done.
However only works on trains that operate on corridors with large loading gauges, not the QR style and maybe, not sure NSW, but I think SW could certainly do something more efficient with its space compared to that applied to the XPT and older trains. Perhaps the former Journey Beyond rollingstock profile works if built and designed from scratch?
Other issue as the article highlights, efficient use of the night trains, which is worse if you are trying to have the best of both worlds, ie XPT. Night and day train. Back to the east coast, I think if you are going to run a night train, its a night train, every night, not a night and day train. In both cases travelers maybe able to go home before after work and catching the train.
Leave Sydney at 8pm, arrive in Melbourne or VV around 7am. This is a respectable time to both leave and arrive and avoids the need to provide dinning cars. By all means, have bar type light meals/snacks that can be eaten in your room or lounge car, but eliminate the dinning car which adds to cost. The train is then parked and cleaned for return the following night. Dinner and Breakfast are eaten off train. As both Sydney and Melbourne stations have plenty of options, then no issue.
For Syd - Bris, then its more of a challenge, 14h for the XPT, assume a sleeper train won't improve on this. I struggle to see how this would prove attractive to have to be at the station at say 6pm to arrive at 8am at the earliest and then this conflicts with peak traffic at both destinations. So no, ruled out.
For Mel - Adel, pretty much like Syd - Mel, but the only question is, is there sufficient demand?
Brisbane - Mel, too long, even on Inland.
Agree with article, using outdated rolling stock or rolling stock fit out which is classic in Australia simply doesn't work.
Finally, who is going to pay for this and why should the taxpayer fund luxury style travel when there is a perfectly good air transport system that will likely do the job (unsubsidised for potentially less than the subsidy per passenger). Yes I would love to be proven wrong and see the private sector start something and be attractive enough to get the numbers, but I suspect you would need a very long train to make it stack up.