A good NLP interface for files would look as different from a command-line as it would from a graphical file manager. You'd want something context-sensitive, with the ability to use pronouns and iterative refinement, some of which would take the place of simple scripting. You'd need to replace many commands with phrases, and many variations on phrases.

Whether you'd get any users is another question.

You might also consider what a command-line interface based on Dasher would look like. Probably not just a simple typing interface. You could extract a great deal of useful information from completion mechanisms, for instance.