I dont think if BA were to buy out BD, the MMC could just look at BA and how many slots it would gain. The trend is for alliance partners to consolidate, this would leave oneworld in a very dominant position in the LON region. skyTeam would fare well with CDG & AMS having good service from LHR & LCY, and skyTeam is arguably the srongest alliance in the regions, with the AMS connections, Star, on the other hand would be weak in LON and almost non existant outside of MAN.
From a compeditive standpoint LH getting control of BD is the best option, and could provide BA with a very tough rival, but VS is likely to have more to fear from LH than BA, at least initially.
I still see VS as the joker in the deck, or more precicely the 49% that SQ is looking to sell. Where will that end up? Perhaps LH would hop on that instead and leave BD to BA, or LH might gobble both... we've all said a VS/BD merger makes sense, but if it were financed and managed by LH, I think it could be a success.