I think you are being somewhat parochial here, seeing it just from the view of the LHR slot pool and the UK regulator. The European market is polarising at an amazing pace, with Air France + KLM + Alitalia in one corner, Lufthansa + Swiss + Austrian + Brussels Airlines + BMI ( +SAS, LOT, Virgin…) in another.
If BA is going to be a counterweight to these two it needs mass from somewhere – and who knows, ‘if you can’t beat them, join them’ might just be an option.