Thirdly the removal of prestige and career progression - for a career railwayman being a guard is a responsible job and one to aspire to - again being made subordinate to the driver and losing control over your own train would not be appealing. Particularly if it can just depart without you and you're now formally a 'nice to have'. I like being able to make decisions and I'm not really up for being instructed..
I completely agree with what you say about why a conductor / guard / TM role is so appealing, but I must point out that for several years before the current dispute, traditional conductors on Southern (of which a couple of hundred are still likewise retained) did not have responsibility for the train and were technically subordinate to the driver on a lot of grounds.
This didn't seem to make the role any less valuable - and indeed the driver would generally just "back up" the conductor if a decision was being made about the running of the train.
The problem came when the second member of staff was made optional, rather than mandatory "eyes and ears". A 12 coach 377 is a much scarier prospect than a couple of coaches in Northern land, in terms of what the driver can't really tell about the state of play inside the train, or what they can't do when they have such a huge crowd to control in an emergency. When you start to get into large three-figure or even low four-figure numbers of passengers, it's truly appalling that there's no mandatory legislative requirement for a fully trained second person onboard - or more than one - outside of the main crumple zone.
Part of this, I think, stems from the unfortunate reality that there is little by way of a truly independent professional body to provide scrutiny of railway safety standards, to which perhaps all safety-critical railway staff should subscribe. The RMT et al are some considerable way short of having this competency or respect. There are relevant railway professional institutions, but they tend not to support an en-masse body of opinion held by the bulk of the workforce involved in the safe transit of passengers.
Remember this is the Northern DOO thread not the thread for general DOO discussion and Northern guards have been given a guarantee that they won't have their salary reduced to OBS levels, so they don't need to fight to get it, they get regardless.
Just a quick correction on this one. OBS basic pay on Southern is considerably higher than conductors on the same network. Some of them are paid several thousand more per annum. Depending on the types of routes worked, commission can sometimes also be higher.
As Carlisle says, converting to DOO on London routes was a matter of putting up mirrors and cameras and bringing in trains with sliding doors, before asking along ASLEF to sign it off. The difference was the CSR radio system which made it possible for the signal box to talk to trains in an emergency. It’s also a myth that BR picked quieter, slower services with less passengers to creep in DOO. Usually, dead branch lines were the last to convert on a general route area. DOO was proven technically safe enough and therefore how long the trains were or how many people were on board was considered irrelevant.
BR and earlier privatisation companies generally picked routes where there were sufficient factors, such as frequent staffed stations and good enough radio systems, to gain public support in the event of any debate having occurred. My personal opinion is that they tended not to be so reckless with the deployment of DOO trains without working out how the public could still be persuaded that there was sufficient assistance available in the event of any incident, for example, even if this could turn out to be somewhat theoretical at times.
As for the extension of DOO(P), it's now somewhat more complex than mirrors (which wouldn't now be used), cameras or sliding doors. There's a lot of trackside and platform work which needs to be done to ensure that all locations meet safety standards. In the case of Southern's extensions towards the end of 2016, this required an intense workload for some staff, and cost everyone a lot of money. I can't quantify the exact spending at the moment, but it went so far as keeping all sorts of random bits of railway running 24/7 with test trains, each of which had numerous staff onboard checking the likes of GSM-R coverage and platform lighting.