There are no easy options for finishing this dispute and BA will (as it is evidently doing) have to choose from the least worst option.
BA forcing a settlement (through SOSR for example, or sacking strikers because action is deemed to be unprotected) would leave a clear victory for BA and BASSA crushed but you have to consider the demoralising impact of that on a very large contingent of crew who support BASSA. Plus there is the wider
PR impact of giving legs to a dispute where the media has largely lost interest.
BA is now negotiating from a position of considerable strength. It has, and will continue to have, everything it originally sought in cost savings proposals. The growth of Mixed Fleet and maintenance of the VCC programme has permanently restricted the effectiveness of any future threat of industrial action and that is important. No-one would have predicted three years ago that BA would have introduced Mixed Fleet entirely on its own terms and built up a substantial volunteer cabin crew workforice. Some obvious troublemakers have been sacked and will not be returning to BA.
The complete destruction of BASSA has never been an option. If BA and Unite agree on a deal that is palatable to the branches (frankly, I think this is unlikley in any event) the BASSA hardcore may crow victory but they have been so indoctrinated into believing everything BASSA tells them and nothing will change that. BASSA will claim victory because they claim this dispute was always about union busting. However, at least when this is over, there will be a elections for new reps (possibly for merged branches) and some troublemakers will hopefully be soon forgotten.