Something stupid I always wanted to do was to make an object-oriented language where literally every single object was a separate UNIX process. The naive implementation would have horrendous context switching overhead from the IPC, but maybe there's a clever and elegant way to use shared memory...
The original idea of Smalltalk was very much that :) Sadly, hardware limitations of the time did not allow Smalltalk to be implemented this way. Erlang was likely the first generally available implementation if the idea. (Now you write in Elixir for the same VM.)
It seems like the reduced overhead of cooperative multitasking (vs OS threads or even greenthreads) is so important that people are writing code entirely differently because of it. Like all those promise/future frameworks in Java etc, or NodeJS which works this way natively.
