I do not understand talk of BA buying bmi. It is hardly likely that SAS/Lufthansa would sell their shares to arch-rival BA. There is also no possible way that the regulators would allow it. What is much more likely is that if bmi were up for sale(which I doubt) then LH/SAS would acquire majority ownership. But do remember that earlier this year LH wrote down the value of their "investment"in bmi. This suggests that they are hardly likely to be interested.
A much more likely alternative to these is that the MAN operations could be spun off into a separate company with that being soled to LH.