Oh, interesting! I wonder if this could be used for an alternative implementation of Nix/Guix's store/profiles. It seems conceptually very similar, but implemented as a filesystem rather than a big bundle of symlinks.
If you're on a well-worn-path you could operate mostly by lookup and only run the code if something doesn't smell right.
Even if it turns out to be perfect in every way though, it takes a long time for the masses to adopt new languages. I think it might be worth finding ways to build consensus around claims like:
> this particular bit of python can be treated like a pure function
...even though there aren't any guarantees built into the language.