The shift in composition of the tiers isn't all that important, it's what the tiers can be induced to spend beyond flying. If people are becoming gold or GGL on the basis of existing flying patterns, the motivation to try to maximise nTP and Avios earning comes at the point where those patterns change and they drop status that they'd come to appreciate. You have to pull them into the spending ecosystem for the overarching strategy to work. If you read the AA forum about the CK customers who'd lost their invitations, you'll see they do astonishing things to retain status, having somehow bound it into their ego and personal brand, but I don't sense the same pull amongst UK business travellers at a high level.

It's not like the situation for hobby GGLs where the first thought in one year was how to qualify the next year for the least spend, in which case we'd have been looking at all sorts of options in the ecosystem I suspect. I've really liked SAF in FB which saves me pointless flying to Sofia and back.

One observation I have been developing is that in fact, if the ecosystem strategy doesn't work well, airlines may be inclined to reduce or remove FF programmes given loads look sort of OK and passengers are paying the fares. This is pretty much what happened at Tesco over recent years. Interesting times anyway.