If every crew member was in Unite, there would not be strike action now, I imagine
I doubt that very much, there are approximately 13000 cabin crew within BA, of which approximately 10000 are in BASSA and maybe 1000 in the amicus branch of UNITE. But only about 3000 are or have been on strike. putting that extra 2000 cabin crew in UNITE would not make the strike any more solid and supported than it is now.
The thing that reaffirms my faith in human nature and proves that BA CC are an intelligent bunch is that so many of them have weighed the evidence and have found UNITE wanting and have turned up to work. This shows an independence of thought that the unions must hate. The leadership must be spitting feathers that since the 70's their power to say "All out brothers" and expect all union members to down tools, has gone and people actually now think for themselves.
Unless you meant it in the other sense, all in UNITE and the vote for IA would have gone the other way and BASSA would have been emasculated. From your previous posts I suspect this is not the case.