The only thing I don't understand, which is what you are alluding to, is why anyone would not want Lauren to be part of the BA list.
Simple really; For FOs -
secondments...five years of very inferior terms with little prospect of a command - moreover, commands implanted from BA, not from within on merit, causing disenchantment and low morale. It doesn't work at GSS at it wouldn't work here - witness recruitment of FOs at minimum experience, with those with options leaving to "normal" airlines, with normal promotion structures. It would be daft to join PL rather than BA mainline. Worried about "inexperience damaging the BA brand"?? - well this is exactly what would happen.
For DECs, I can see no reason.
The argument for keeping PL completely separate is compelling; witness GO - An excellent outside CEO (Cassani) and a motivated pilot force = a very successful airline. Of course, BA couldn't allow the prodigal child to prosper on its patch, so it was sold for way below value. BA influence is
poison to organic growth and innovation.
Secondments are a flawed and distasteful distortion of the pilot structure. A ban of W flights entering the UK has merit, as it would be a breach of scope.