An interesting sideline to this is that VS could get instant *A membership (whether or not the other *A airlines wanted them!), if the deal was structured as a reverse takeover of VS by BD. That in itself would be worth a decent chunk of the takeover cost. There may also be other savings to LH if it is under pressure from inside *A (if BA gets BMI) to offer a status match or miles transfer.
And it would make my 1m VS miles (which is what I would presumably end up with) be worth having ...!
Lots of other upside here as well, eg being able to put Tesco into a *A airline.