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...
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.
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.