For what it's worth I don't think BA will be sacking anyone either. My opinion is that BA are attempting to use the 'moral high ground' to win this argument. They have to be able to show they have done everything possible to come to an agreed settlement, so plenty of negotiations, ACAS, various offers etc. Whether you agree that they have actually done this is another matter, BA will stand up in court and persuasively argue that they have ticked every box but to no avail, leaving them no choice but to impose.
Sacking striking workers would, as has been mentioned, be illegal. Unlike the price fixing which was obviously meant to be kept quiet, there could be no illusions that such a course of action would remain unreported for any time - it would be all over the mail/sky news as soon as it happened. This, in my opinion, does not fit with the way they are playing the situation.
I'm sure they will play hard ball if strike dates are announced - crew will be informed in blunt language what they will lose - ALL pay for strike days, staff travel etc. Arguments about staff travel being contractual are irrelevant. BASSA state that 'a test case would need to be brought'. Not that they are in the process of doing it, just that it would need to be done. How many months would it take to prepare and fight this case? Even if you win, that's still months without staff travel for all strikers and organisers (BASSA Chair included). Of course it is normal in these cases to agree the re-instatement of any lost perks as part of the return to work deal, whenever that is...
All crew reporting sick can expect to be treated with suspicion and will need to prove it. This will be seen as harsh treatment by those genuinely ill, those who think BA is a tough employer now will be surprised how much harder they are when you decide to withdraw your labour.
Just my opinion of course, we'll have to wait and see.