I assume this will be lower cost through plastic casing, M1, and low RAM/storage.

Currently the M1 is sufficient for 90%+ of the population (IMO), it is the RAM/storage that will outdate most Apple computers. If Apple sells this in the $599-799 range with 8GBs of RAM that would be a solid offering for most K-12 schools.

They really should just enable mac apps on the iPad, and let that be the low-cost MacBook.

There is something to be said about the laptop form factor and macOS enabling productivity. That said, I would definitely see the guts of an iPad being put in the frame of a laptop with macOS.

MacOS generally needs more ram than iPadOS because iPadOS can be more aggressive about pausing and closing applications to free up more ram than MacOS can be. I think some modern iPads are still at 4GB when that's too low for modern MacOS.

The Air and 2 port Pro are very close to being the guts of an iPad Pro in a laptop chassis with macOS anyway.

Different input devices really do need different UI controls, if you want a comfortable and polished experience. You can just do it anyway and expect the user to 'deal with it', but you end up with experiences that people just don't really like: https://en.wikipedia.org/wiki/Microsoft_Tablet_PC

an iPad with the Apple keyboard brings input parity, so really nothing holding back running Mac apps.

An ipad with a keyboard would still have an issue with the control design disparity between touch input vs pointer input.

We already have... they've destroyed reparability by soldering in the SSD and the RAM, and they turn into soft-bricked e-waste every time someone donates one and doesn't remove their Apple cloud account first.

They reduced the need to repair due to disk or RAM failure by getting rid of the connectors.

I am not claiming they did this out of the sweetness of their hearts, but I do challenge your first point.

I believe apple could fix the “didn’t log out of iCloud” problem if they want, even if only through through some special apple-only refurb process. They would have to have some way to figure out n if it were stolen or legitimately discarded. But they have no incentive to do this.

I've never seen a disk connector failure, but I've constantly seen disk failures. Soldering your disk to your mainboard also makes the cost (and odds of failure) of data recovery much higher.

Obvious strategy for price segmentation: it runs full macOS but can only install/run apps from the app store, and has no Terminal.app. At a stroke that partitions the market so developers and admin UNIX lover types can't buy them. Pro media users can't either because not enough RAM. But it runs Safari and iLife.