A short answer would be that dozens of projects like this already exist and have existed for decades (scsh was mentioned in this thread), and they aren't widely

A short answer would be that dozens of projects like this already exist and have existed for decades (scsh was mentioned in this thread), and they aren't widely used as shell replacements: https://github.com/oilshell/oil/wiki/Internal-DSLs-for-Shell https://github.com/oilshell/oil/wiki/Internal-DSLs-for-Shell https://github.com/oilshell/oil/wiki/Alternative-Shells https://github.com/oilshell/oil/wiki/Alternative-Shells It doesn't mean they aren't useful, but we still need a better successor to Bourne shell / bash.