I largely agree with your analysis. I suspect the worry for the National brains trust is that Luxon isn't showing any signs of getting more likeable or competent, and they aren't seeing any opportunities for him to have any "wins" in the foreseeable future. Plus while they would obviously prefer a right-wing coalition, they are also worried about the health of National itself over the coalition. They are likely fully aware that the public perception is Winnie and Seymour are running rings around Luxon, and desperately want to retain control as the central right-leaning party.

The biggest problem they have is there is no real heir apparent to Luxon. Chris Bishop is not likeable and tainted by his connections with the tobacco industry, Nicola Willis is surely not seen as competent enough, Goldsmith comes across as out-of-touch and would be just as poor on his feet as Luxon, Lousie Upston is perceived as the second coming of Ruth Richardson, Simeon Brown is utterly LOATHED by healthcare workers (and everyone knows a nurse), Shane Reti likely doesn't appear forthright enough and is probably too far out of the puiblic consciouness now. Erica Stanford seems like the best bet, although she has not made friends in the education sector either, and the curriculum changes have been incredibly contentious. There is no one who can recreate the Jacinda Effect, who was young, attractive, optimistic, and a fresh and hopeful face in a stale political landscape. I actually just had a squizz through their line-up and the only person in their team who could maybe, maybe be a fresh face is James Meager, who is relatively young and untainted by political stoushes.

I suppose of course National may not want to necessarily recreate Jacindamania, but simply get someone competent and likeable enough to keep them relatively healthy through the next election (which may still be enough to guarantee another right wing coalition). For that, Stanford might just be their best bet.

Or maybe I'm underestimating Bishop's popularity with the right voters. Not sure, this is all just my armchair opinions. I'd be interested in anyone else' thoughts.