Have we forgotten the cautionary tale of Steve Ballmer's Windows Phone boondoggle already? Ballmer wanted to use the same codebase for desktops, laptops, phones and tablets.

It goes back further than that too. Microsoft bought the Sidekick and squandered their lead by bringing it onto the Microsoft platform.

I'm reminded of this quote: "A Foolish Consistency is the Hobgoblin of Little Minds."

Laptops and tablets are different devices. We should stop trying to merge them. Every time we do, we end up with something that is a worse version of both things. Tablets need a battery. If the display is detachable, then that creates a weight problem for the laptop. The tablet keyboard is worse than any laptop keyboard.

I said over a decade ago I thought Apple was smart to just have a tablet OS as well as OSX. Don't spend 3 years trying to merge those things. It's a waste of time and gains you nothing. Even the tablet and phone OSs are somewhat distinct (but a lot less so than with OSX).

I always thought Eric Schmidt (at the time) did the right thing with ChromeOS and Android too. There were always questions from people seeking faux "consistency" like "why have 2 OSs? Shouldn't we merge them?" Again, phones and laptops are different things. Let each OS evolve and see if one emerges as a "winner". Otherwise, leave them alone.

Chrome OS does a fairly decent job with the transition now. I used to use a Lenovo Duet at times. If you had the keyboard / touchpad attached, it would go into the usual desktop mode with floating windows. If it was just the tablet, then windows would tile. Gestures for the usual tasks. It wasn't a complicated system but it did work fairly smoothly.

And then there were the checkboxes which allowed you to extend the OS beyond Chrome OS's initial limitations. Enable Android. Enable Linux. Enable developer mode. But the user (or administrator) could ignore those checkboxes and keep the machine in a fairly locked down state.

Keep imagining a similar abilities on iPads. A seamless transition from desktop mode to touch and back again. With options allowing you to make it into more of a general purpose computer if you want. But the options can be ignored in favor of the walled garden, if that's what the user or school or corporate owners want.

First let people seperate photos into different folders....

Well, Microsoft tried this, it was called Windows 8. It failed miserably.

Windows 8 failed because it tried to merge desktop and tablet UI paradigms.

Switching between entirely different and separate "UI personalities" could work.

I don't think the pointer vs touch UI is the main thing that people have in mind when wishing for macOS on the iPad though, instead a "proper" UNIX-style filesystem and shell, and the ability to install any software outside the app store via a package manager and without Apple's nanny reflex getting in the way.

That's basically running two OSes. Don't think that's a great idea. We have enough cruft.

So you're saying my Steam Deck, which has both a "game console" UI and a desktop UI mode and lets you switch between them, is somehow running two OSes? Weird argument.

Sadly it did, I had one of the OG Surfaces and really liked Windows 8

I mean, their strategy was awful. They replaced the start menu for the first time with a whole-screen abomination that ruined power user workflows. They made the desktop TOO much like a tablet, it seemed like they wanted one interface for everything.

Apple is very clear about their product differentiation and would never make macOS and ipadOS exact copies. Case in point: when they brought cursor support over, they painstakingly engineered it to work differently and snap to objects on the screen. I think if they did OP's suggestion and had a macOS screen show up when an iPad is connected to peripherals it would actually work out well.