Comment by okanat

This is simply too complex. There are quite a bit dependencies on Glibc and other GNU-based behavior.

What you're actually asking from them is creating a new Android or Chrome OS i.e. recreating the entire userspace. "Just split up musl" will not work. How the system headers work needs to be redefined. This is basically a complete redefinition of entire API of all Linux programs and libraries. Which library will supply unistd.h or any of the sys/whatever.h? Any interdependencies? I think even POSIX itself can be hostile against this. So the fix will have to deviate a lot from that (that's probably why Windows cannot be made POSIX easily either).