I've never suggested that it would be a suitable model for all services, clearly it wouldn't be suitable for stopping services on the Weymouth or Portsmouth lines. A train running pmh,PMs,ftn,hav,pfd,hsl,gld,wok,wat or poo,bmh,bcu,sou,soa,win,wok,wat could conceivably be run like this as all those stations are staffed (though may need some modifications.
For stopping services yes body side cameras would need retrofitting and monitors in cab and without some very clever engineering there's no room in the cab for monitors to be easily available to driver so I don't see retrofitting the entire fleet would be viable.
My point is that people just rule desiros out of the equation too easily.
I'm pretty sure you're aware of my view on this anyway and I believe every train in passenger service should have a fully trained guard on. I'm not particularly fussed about who opens the doors , but it needs someone on the platform to close them ideally in my opinion.