> I wonder what a hobby OS would have looked like it if it assumed nothing
There's lots of stuff that was around in the 1960s that became dead-ends because everybody piled in on another way of doing something, and then things got optimised for that way, then every other way was less performant, and soon the lucky one way became the only way.
I've never really had much time to explore these early ideas from well before I was born whilst working, but definitely think it'd be a fun way to spend my time when I eventually retire - to try to recreate some of the stuff from that era that got forgotten and see what it could be developed into nowadays.
For example, just watch Douglas Engelbart's 1968 demo [1] for some ideas - some of the things presented in that took decades before it was rediscovered and implemented on systems available outside of research environments.