You'll compile a lot out, sure, but I don't understand from the discussion why it can't be done. I understand why it's hard, why certain people have no interest in it, and why using a 64-bit address space is important for security defense. But nome of that seems to make it fundamentally impossible.
Depends on how you balance take advantage of modern hardware with be somewhat useful for hobbyist desktop users.
If you think “somewhat useful for hobbyist desktop users” means booting from UEFI, supporting USB-3 including hot-plugging, and doing power management well on generic hardware, I don’t think there’s any chance to stuff everything on a floppy disk.
If you’re willing to remove device enumeration, effectively building a different kernel for each choice of to be supported hardware, work with just a tty over a serial port, and be forgiving a lot on the “Unix-like”, it’s quite doable (example: http://lng.sourceforge.net/, a ‘Unix-like’ OS for the Commodore 64). The “somewhat useful” would suffer, though, and one could argue that isn’t “Unix-like”.
There may be something in-between that adds enough usefulness to make it “somewhat useful”.
