I'm not sure what you mean by this ERNEST as conductors still have to have a Safety Critical certificate (although this is part of the dispute). Any 'manager' doing their work will also need to be qualified. As you know it's not just a case of shutting the doors and going 'ding, ding'. If...
As I said they haven't got that many managers. Of those some will be on holiday and some will be required to do other duties. Last time I looked they were snowed under with a backlog of work due to shortages of staff. A lot of that work can't just be left for another day so Southern won't be...
They haven't got enough staff now let alone managers to run a service mate. Trust me, using managers will be fraught with all manner of problems unless they tear up the working schedules (diagrams) and run yet another 'emergency timetable' that probably won't work. Even if they did use managers...
Will they? Which trains don't have conductors along the Coastway? (They can get round this by calling at 'Manned' stations only I grant you but I doubt they will)