Well thought out post.The trouble with betting on future Apple releases is that we don't (in general) know when (or even if) they will happen, so it's a risky proposition to plan your hardware purchased based literally on rumours.
I have the MBP14 and while I don't use it in clamshell mode, I don't use the screen when plugged into external monitors because I have to place it on a second disk due to space limitations, where I can't see it.
The reasons for getting the a new MBP instead of a future Mini are:
(1) It can be bought *now* rather than at some unknown point in the future
(2) I want the same powerful machine when mobile as well as at my desk.
(3) Not having the hassle of maintaining 2 machines and ensuring that they are in sync with the same software and data (although with cloud storage, this is a minor task these days)
(4) A future Mac Mini with M1 Pro/Max will probably only be $400-600 less than the equivalent MacBook Pro, based on the current price differentials between M1 Mini and MacBook Air/Pro. You won't get an M2 Air for that difference, so a 2 computer solution will be more expensive.
If you never travel with a laptop, or have no need for a powerful mobile machine, then a future M1 Pro/Max mini plus an iPad could be a good solution, that works out about the same price, and gets you two devices for different uses.
I also have an iPad Pro 11, and think there is a big difference between and 11" and 14.2" screen in terms of real-estate, particularly if you put both screens at the same distance. But I agree that you generally use an iPad much closer to your eyes than a laptop, so it probably fills the same visual field. The ergonomics are completely different though, which is where the iPad shines. As for using the iPad as a stand-alone computer? Remember the original small 11" MacBook Air? It has tiny screen real-estate..very cute, but a bit impractical for large documents, spreadsheets, code etc.
The resolution on the ipp 11 is higher than the 11 inch air was.
For me if it is emailing ,notes, basics simple productivity then it would be easily done on my iPad pro 11 with MK.
Given the overall size is smaller it suits closer to me then the 14 and so the size differential as your said is not so different.
The 16 is a big beautiful beast. I don't mind the extra weight at all and that screen and speakers make watching anything better.
The extra real estate is not so useful in single track things like email or web browsing however.
But for video watching our photo/video work the extra screen helps.
I find it somewhat hard to clearly describe but when I watch something on the 14-in I feel like I'm watching somethingj on a laptop. However when I watch something on the 16-in I definitely feel more immersed in what I am watching. I see less of the surrounding environment. I guess it is akin to sitting closer to the front third at a movie theater versus the back third. Overall you still see the same content but one is much more immersive.
Because I can take the iPad off of it's keyboard case, I can get a similar immersion just by holding it closer to me then I could with the 14 inch MacBook Pro.
If I only could choose one device from the three then the 14-in would be the best overall compromise as it is not much bigger in footprint than the 11 inch iPad Pro and keyboard and is this very transportable. It also provides similar power as the 16 inch and similar battery life to the 11 inch iPad Pro.
I just feel that for many people who own multiple Apple devices, that it is better to have larger degrees in size difference between them so that their use cases don't overlap so much.
That is why to me owning a 12.9 inch iPad Pro and owning a Mac laptop that is under 16 in makes no sense as the screen real estate is near identical. The weight in fact is heavier on the iPad when combined with magic keyboard.
If owning a MacBook Pro of 14 or less inches or the MacBook Air for that matter, then a better companion device might be the iPad Mini.
I also see your point on just having one device rather than having to deal with the sync issues of both. However, when I talk about the M2 MacBook Air and the M1 Pro Mac Mini models these are not things that are maybe coming down the pipeline at a later date but are quite likely going to be available within the next month or two.
If you factor in the average price typically of a MacBook Air and then add in the price of a typical Mac Mini I could see the combination not being more than 2,500 us. That is almost identical in price of to what a 14 inch MacBook Pro with 10 core CPU 16 chord GPU and 1 TB of ram would have.