I work on the railway.
I speak to other grades and listen to what they say and what's happening in the real world.
And it's not what a small minority of people who live in internet forum lala land say.
That's MY evidence, take it of leave it but I really don't care
A fairly large number of members of the public want a second member of railway staff (i.e. not a rent-a-thug; someone who knows what they are doing to assist with things like connections, tickets etc as well as keep them safe) in the passenger cabin to assist them. My sister is one such person.
I very much doubt they care (or in some cases even know) whether that person operates the doors or not, and I suspect they would be equally satisfied were that person a traditional guard, a guard with driver release, or an OBS.
Indeed, I rather suspect most of them would prefer it to be an OBS who is actually in the passenger cabin at all times over a non-commercial guard hiding in the back cab.
I suspect they would be entirely satisfied with the Southern model, or indeed the similar Strathclyde one. Or even something a bit different like the guard dispatching by waving something to the driver but him being responsible for closing up safely, as you get in some countries. And if their train was probably going to be cancelled because that person was ill, I expect they'd also rather it ran, on that occasion, without them.