Now that that self-opinionated git has disappeared back to his igloo to freeze his nuts off, those who know what they are talking about can continue without irritating interruptions.
Itch, some 'case history' on the base/fleet reductions: about a decade ago an airline now Connected to yours (there's a clue there) got rid of two entire fleets and a whole lot of bases in one fell swoop. Pilots were laid off, although in many cases with back-hand deals with another airline to take a select few. There was a tribunal case where it appears to have been made clear that if your base or fleet was going you were at risk, regardless of any 'seniority' system. Going on that it appears that the answer to your points 1. & 2. are that you are at risk. Your point 3. would be a bit more of a problem where some system, acceptable to employment law, would need to be used to select who goes. That all fits in with mad_jock's comments. One point is that any system for selecting people for redundancy should be set up before there is any risk of redundancies to be looked at very favourably by any tribunal. Selection processes that are cobbled up as the threat for redundancy occurs are likely to be picked to pieces by any tribunal. Maybe that is why the straight fleet/base system is being used in your case: it is straightforward and unlikely to be picked to pieces if there is any tribunal.
BALPA's role? It should have been to ensure that a viable selection process was in place well before the threat of redundancies and that that process would be financially viable, i.e. it wouldn't cost so much to carry out that process that it would drain on the airline's resources to the point that they'd have to get rid of a greater number of pilots to 'fund' the costs incurred by the redundancy selection process (e.g. if lots of pilots need to be retrained onto other fleets or transferred to other bases at the airline's expense). When redundancies are threatened, BALPA should be looking at ways of reducing the number at threat by helping the airline to keep people. In BMI they appear to have helped save several jobs by getting all pilots to agree an effective pay reduction in order to fund the retention of those pilots at risk. Have they been working on either of these in your airline? Also, the effectiveness of BALPA in your airline will only be as good as the effectiveness of your reps. If you're a member you could have stood to be a rep and you most certainly should have voted for candidates. Often there are reps who are only in it for themselves, it is up to you as members to see that and stop them. So, BALPA is only as effective as its members. So, are its members 'fit for purpose'?
And as for those that complain about the downward trend in Ts &Cs, well when the money runs out, so do the Ts & Cs. If you were working for any other type of business and you saw poor business practices, the sensible thing to do would be to jump ship early and get a job with another (competitor?) employer that seemed to have his corporate business head screwed on the right way. However, too many in the airline world are shackled from moving by that curse called 'The Seniority List'.