I think the issue of union membership and this strike are different. BASSA, love them or hate them, do a lot more than look after and organise strikes. The relationship between BA and BASSA and BASSA and their members needs to be redefined but I really doubt whether it is likely or desirable that the crew are not represented by a union in some way. I suspect it is also unlikely to see the union representing crew to be changed for another one.
Striking crew have pointed out that they are BASSA, well so are the union members who voted no and who are working during the stoppages. Norman Schwarzkopf after Vietnam said he nearly left the US Army bur decided to stay in order to effect change from within. Ultimately this is what must happen with BASSA, its' members must effect a change from within.