> You could build yourself a Scheme or a Common Lisp on top of it if you wish.
No offense, but if it were Common Lisp I would take a look, but I don't have much interest in learning a one off language.
Sounds like you're having so fun, though, so good luck!
The goal is being able to replace every single part of the runtime/interpreter if you wish, but the OS itself starts with the fewest functions/features possible. cons, lambda, and the other usual suspects, a way of running actual native machine code, the homoiconicity of LISP, a runtime-editable image, packed into a UEFI binary.
You could build yourself a Scheme or a Common Lisp on top of it if you wish.