A single loco hauled consist + powercar will not happen and id hate to see what would happen if it did. I can't seeing the government buying some massive loco and seperate stainless passenger cars.
The advantage with push pull and dmu is you have backup traction and hotel supply's. If one engine packs it in you have a spare (as internal combustion engines are prone to do in any application.
I favour push and pull diesel-electric over dmu diesel-hydraulic as there is less noise and vibration, less components to break (blow a hydro line and it's no go and a good sized mess for someone to clean up). Electric traction motors are protected by circuit breakers, and nearly unbreakable. It's quieter over long distances which is the main point, just the odd bogie squeak, from inferior track conditions.
Remember also the XPT was designed with the unions hanging over the builders shoulder. (remember the 5 notch power controller over the 8 to prevent them hauling freight) and much to my disgust they will be hanging around the next time as well.
Where did you get the rubbish from re problems with the union over not 8 vses 5 notche power controller? That is the first time I have every heard of that one, & having been an XPT driver & divisional councilor/branch secretary of the AFULE, the only aspects that were on going regarding the XPT which at the time the enginemen were flat out finding room in the cab owing to the polititions & other hanger onners being in there, in many cases they wanted the fireman out & to sit in the carriage during tests on them.
The 5 notch throttle was a standard type that incorporated dead man as did the brake valve a standard item I believe on the HST in England, & was part & parcel of the power cars, no debate was had over that. Its the same as found on EMU trains, DEB sets & other DMU's that had combinations of between 3 & 5 notches to apply power to them.
Just because you favour push pull or some other set up does not make you the expert in this debate nor do you have the money buy any replacements, Thankfully as goodness knows what you would inflict the driver with in the cab.
It took years to get decent seats in deisels with those in power including one employee representative on the old PTC & SRA board who had the desire to remove back rests from the seats to stop the crew from dozing off, if they did they would fall to the floor, wonderful employee rep he was.
As for the overall staffing of the XPT, they were a straight replacement for the then loco hauled airconditioned trains with full buffet service including cooked meals & take away items, thus the full staff as per the old trains were applied. There was in those planning days no issue what so ever with having reduced manning on them, as they were Wrans Election toy, or Expensive Plastic/Political Train/Toy.
Once they got in & the single driver issue came up, the decision that was handed down by the Federal Industrial commission was that the XPT was based on, & affectivel was the same train as the British HSTtherefore the decsision handed down was the XPT was to operate under the same conditions including miles in the cab & based also on speed. Trains that were working up to 160Km/h were to have a single driver in the cab, if the train was to run at speeds over 160Km/h then it was to be manned by 2 fully qualified drivers with shared responsibilities.
Time you looked at things through clear understanding glasses & get the facts in areas where they are needed.