I suggested on Mini-Microsoft about 10 years ago that Microsoft do an 'Apple'. Apple took a free OS from BSD and put their own GUI over the top of it. I suggested that MSFT do the same sort of thing, that being to put their Windows GUI on top of the Linux OS instead of using the Linux X11 GUIs. This had the advantage that the underlying OS base would no longer need maintaining by Microsoft, and all their coding effor…
Besides, in a sense, Microsoft did this when they moved the desktop product line to NT. It wsa a similar compatibility break and a similar improvement in stability and switch to a robust, multiuser, preemptively-multitasking kernel as classic Mac OS to XNU; it's just that the kernel Microsoft already had in house was NT, and the one Apple/NeXT had was XNU.