It's happened! We have some internal magic that lets us run ml directly: ./my_bash_script_replacement.ml, and it makes replacements fairly painless.

But we don't do it often. Each language has its strengths and weaknesses, and the constraints of a small script tend not to change that much over time. The script either starts other executables and pipes some text around, or it does some computation. The choice of which to use is often (but not always) clear.