Is BALPA fit for purpose?
NO!
They were well versed in this problem 4/5 years ago when Baby went through the same thing.
The PN was the same PN for Baby as Flybe had until recent times, your CC would have or should have known about this years ago, the PN definitely did!
The PN and CC should have negotiated a new redundancy policy years ago, that was acceptable to both fleets and all on the seniority system. Then it would have come as no surprise.
Whilst I completely agree with comments over why you are being made redundant, greed etc.... In this instance BALPA and no one else is responsible for allowing an outdated and questionable policy ( due to new laws) to remain for so long after it became clear it wouldn't work.
Another thought, do you think BALPA would risk being sued by pilots from other companies who were made redundant under a matrix system just to protect LIFO in Flybe ?
Gentleman / Ladies BALPA have yet again failed to act in good time and let you all down.