I don't see a 2nd set of doors necessary and really just another thing to limit the design and break, especially on intercity services where stops are further apart. Where NSW was lacking was the ability for pax to open the doors as required (actually V-sets had this), rather than all open, lets have 8 cars sit at the station bleeding their AC into the heat/cold. Qld started out with Pax initiated individual door opening. Ideally the doors should then after say 30sec after detecting the last passenger movement the doors should close.I don't understand your argument here. The V sets have internal vestibule doors that do stop the a/c from the rest of the car, as you put it " the bleeding of the a/c into the heat or cold". I believe the NIF cars do not have this, so when a set of doors open, the a/c from the whole car is open to the elements. Will be wonderful for the passengers sitting at the very ends of the cars when the doors open at Katoomba with a howling gale and minus 5 temperatures in the middle of winter.
FYI: I spent 8 years sleeping in V-set 10 times a week so I'm very familiar with them.
The V-set has the intermediate door and semi-manual main doors, ie, unless someone opened them at the station the door remains closed.
The V-sets and any other train on the Inter-urban runs have a low density stopping pattern, that is in there 3h run they have roughly 28 stops or one every 6min, vs 2-3 min for suburban sets, so the doors open less often and if you factor in the short stations some doors won't open for over half the stops.
So doors open less frequently and only as needed. So the opportunity to bleed AC air into the outside world is far less than the suburban sets and hence they really don't need the internal door and if you look at the unloading of a V-set, its a F'n pain in the smeg for pax, especially those with things already in their hands and just slows the whole process down. Woy Woy station it used to take 1-2min, sometimes longer to discharge a crowded V-set. Likewise Hornsby, this dwell times are no longer acceptable. You can also not build a train with such a narrow entrance into the main cabin due to DAA issues.
Additionally the vestibule of a V-set was quite noisy compared to the cabin so the internal door helped reduced the noise levels alot. Train designers have moved on from this.
The V-sets were originally designed with booked designated seating in mind, hence their seat numbering, I'm not sure if it was every used, but it certainly wasn't come 1982. The concept design of the V-set was from an different era with different technology and despite still being one of my favorite trains, its days are numbered and the design is no longer fit for purpose.
As far as I understand NIF have sensors that prevent opening if there is no platform at short stations, so you won't get loss of AC.
As I said for all other stations and this should apply Sydney wide, doors should be passenger activated with a button like ALL QR trains and after X many seconds of no passenger movements automatically closes. This solves the whole AC issue and prevents the need for an internal door. The problem how do you bring a new train with this concept to the Sydney masses now? NIF not an issue has a smaller audience that can be quickly trained, once the NIF is in a settled you can apply to future stock to Sydney and potentially retrofit older stock as QR have managed.
This is an area for once QR are 40 years ahead of Sydney, that and AC trains.