The problem with these flights is always going to be frequency (or rather lack of it).

With the proposed frequency connections at LHR are going to be too long in a lot of cases meaning people will often choose BA anyway.

As for competing with BA for the business travellers, without similar frequency to BA their is no incentive to pay high end fares which is the only hope a full service carrier has of breaking even on UK domestic routes.

Following the purchase the availability of these seats dried up as BA stopped offering these to ‘non’ One-World carriers

I’ve just booked GLA/LHR(BA)/LHR/HKG(VS) for my parents through the VS website. BA interline with dozens of non-Oneworld airlines.