Apple has the technical capability to make a Macbook that is separable. The screen comes off and makes an iPad.
It also has the technical capability to make a bi-modal OS.
OSX with a HW toggle switch that allows OSX/iPadOS modes. The switch could be nearly seamless. The unlimited freedom OSX mode is an overlay FS on the iPadOS mode. Change anything you want, run anything you want and when you flip the switch, the OSX apps are frozen to disk, the overlayfs unmounted, and you still have any iPadOS apps running. Flip it back, and the OSX world resumes as it was.
But you can't have this product, because the marketers at Apple know that you would never buy an iPad again if you had this.