I wonder if there could be some way to sign a dynamic library to allow it to create direct system calls and then pass that as a kernel command line argument at boot?
It is not the only operating system in the "unstable kernel interface" group though. Linux is actually the only one with a stable system call interface.
I've written somewhat at length about this:
I appreciate the feedback. My intention was to maximize the use of space with big fonts even on the desktop but there's no point if the resulting text is unreadable.