but if I got on a flight and found a VCC of any kind - ground staff or pilot - working up as Purser or CSD, I would be telling Ops that I'd like to offload myself
Ask around...... you will find that VCC's working as pursers or CSD's will have been specifically trained for that role and a great numbers of them are former CSD's and pursers and probably have been such for longer that you have been flying.