What a conundrum it is. So what do you do if you are a BMI pilot in the pool, do you decline an offer in the hope that you will be automatically taken on with enhanced seniority or do you accept and find that former BMI pilot colleagues are absorbed above you in seniority terms. It happened with BCal.
It would be difficult to imagine that BA (IAG) will sack the pilots since it is almost inevitable that there will be horse trading with the goverment in order to keep a maximum number of slots and so I think "what to do with pilots" & other staff will on the contrary feature heavily.
And then of course the little matter of cabin crew, MF or WW/EF but that is a subject for another place.