Ask HN: Should Microsoft rebuild Windows as a *nix based OS?

The whole point of NT was to provide Win32, POSIX(UNIX), and OS/2 all atop the same kernel. No need to rebuild it, NT was built like that.

https://en.wikipedia.org/wiki/Windows_NT_3.1#Architecture

Nothing stops Microsoft from putting an entire GNU or BSD userspace atop their NT kernel. They probably built the proof-of-concept 15 years ago.

EDIT: Considering that they used the BSD network code to put TCP/IP in NT 3.1, it's likely that they had at least a minimal BSD userspace running atop the NT kernel circa 1991/1992. That could have meant x86, Alpha, or MIPS:

https://en.wikipedia.org/wiki/Berkeley_Software_Distribution