"It is not because BA want to sack crew" - disagree. I don't believe BA want to sack all striking crew. But if Unite handed them the opportunity to sack the "ring leaders" \ key extremists then I think they would take it.
As I asked above - why would BA want to stop "illegal" \ "unprotected" strike action now which only allows for protected strike action in a few months that hits summer bookings?
I think that course of action would result in problems if any of the extremists or ring leaders went for an ET. It would have to be all the strikers or none realistically.