> On a iPad or iPhone I'm willing to accept that

But that's it right here. It just takes boiling the frog slowly enough. The high powered M-powered iPads are already testing the waters of what people will accept for work (I don't think they're aimed purely at content consumption like the "smaller" iPads). I think Apple can afford to wait because they don't need to cannibalize anything today, and because the replacement isn't strictly a superset of what it's replacing, it comes with the caveats you mention. As soon as the market is ready to tolerate more lock-in, it might happen.

Enough people do just emails/Teams/Office for work so plugging in an iPhone and turning it into a desktop with mouse, keyboard, and external screen(s) can tick all the boxes for usability. Or an iPad with keyboard since similar sized devices were historically used for portability. Most work devices are locked down anyway, no root, no software installation.