I suspect that the stand in CC will get a lot of moral support from passengers who realise that they're going beyond the call of duty to get them to their destinations. As someone else commented, there's likely to be a bit of a Dunkirk Spirit on board.
Absolutely. I'd go further, I'd go out of my way to travel on a BA flight as opposed to another carrier simply to show support.
If BA get enough staff volunteering, it could be a real
PR coup for them - and might well go a fair way to restoring confidence amongst the public.