pkgsrc already supports Windows Services for Unix, it may well work on top of this too (though I haven't looked at Gow yet and I honestly have no idea how it differs from MSYS).
But when I think "Unix-like core plus package management on Windows"... well, Cygwin is already there.
SFU/SUA only work on enterprise/ultimate versions of Windows. Also, pkgsrc is reported to work, but who actually tries it know it works pretty bad and it requires lots of manual patching.
But when I think "Unix-like core plus package management on Windows"... well, Cygwin is already there.