Contrary to the prevailing idea that BA has no interest in Swiss joining the alliance, I think BA has a number of holes ot fill in the European network. Swiss could be very helpful attracting German-speaking clientele from the Austrian/German/Swiss market whose only other option is the current LH/OS monopoly. BA has only one major hub in Europe.
There are synergies to be one also for BA when clients choose LX over OS/LH for e.g. their Vienna to Geneva trip. Almost everyone I know in Austria and Germany is a member of *A for the single reason that on their home routes there is no alternative to OS/LH. If Swiss were there to compete, the same clients flying Swiss from Stuttgart to Geneva instead of LH would then fly BA to Asia and the US.

Long story short, I reckon Swiss should be to BA what OS is to LH. A feeder.

Unfortunately Swiss just ordered 13 (if I remember correctly) longhaul Airbus, which kind of contradicts the reposition necessary to join oneworld.