DOO was never going to come in on Merseyrail. Aside from it being Liverpool (which has it's own culture around work, unions and employment), the drivers knew both Chris McGhee and Martin Zee personally and what happened to both of them - one in prison and the other dragged through the courts on an utterly nonsense charge, essentially runing his life and it appears ending his railway career even after being cleared.
No driver who knew either of them is going to want to be responsible and as the court in the McGee case stated, legally liable for safeguarding drunks and crowd control on platforms, nor the myriad of dangers in the dispatch corridor. I'm not going to defend the actions of McGee, but aside from the dispatch incident, the summing up of his case included the judge castigating him for failing to deal with the welfare and safeguarding of the girl irrespective of the accident. Without a guard, a DOO driver is legally liable for this.
Coupled with the Stephen Murdoch dispatch case and West Wickham where a trainee driver dragged a woman under a train, and with the onus on lone drivers being responsible for managing crowds and behaviour on stranded trains these days, it's a non starter.
We've moved on from the 80s mentality of "you're on your own on a DOO train", with a driver simply relying on gaining interlock, and simply ignoring crowding issues on platforms or people getting assaulted, vulnerable minors, the disabled on trains - and rightly so. Unfortunately the powers that be can't simply then turn round and demand that this same lone driver is made legally liable for everything on top of it / or the scapegoat for everything, when the public rightly demand higher standards.