Regardless of how much people like / dislike BA,BD,VS - surely it would be better if BA were to buy BD - Britain needs a national carrier with slots comparable to German and French flag carriers who have far greater slot majorities at their hub airports than BA. I think enough British Airlines have fallen into German hands already this year!
Certainly not - healthy competiton breeds better conditions for passenger, more choice, lower prices and better service. The days of national champions are recognised in all economically-literate countries to be far in the past.
It benefits nobody other than vested interests and shareholders to hold as many slots as possible at one airport; while connections in some areas might be improved, competiton far more quickly identified new routes, aids passenger experience, and permits greater flexibilty in changing circumstances.
(So exclude from the above - Alitalia etc)