Windows 10 does it perfectly.
If you haven't used a Windows 10 tablet for any amount of time, I'd suggest trying it out. I've used small and large Windows tablets for many years and have yet to find any big complaints about the UX.
In your opinion ofcourse. I find Windows 10 tablet mode ghastly, especially compared to ipados or ios. The only nice thing is that you have a real OS. If this iPad would run macos or windows, I would leave laptops and phones behind from that moment in. But alas. Maybe the 2nd gen surface X?
I suppose everybody here should always preface their comment with IMO...
Good thing that if you don't like the way Windows 10 looks, you can easily change it. Other than that, functionally, everything just works and I'd challenge you to say what doesn't.
Attempts to get there tend to dumb down and limit the functionality of the mouse+keyboard experience.
I guess the obvious option would be to let Pro users switch an iPad into a 'MacOS mode' with the full desktop interface, mostly relying on an additional keyboard+mouse. But I can't see Apple going for anything like that. They're more likely to push the desktop interface more in the direction of iOS...