[zeveb]

Yeah, except that inevitably one does end up wanting some element of Turing-compleness, hence the Jinja templates used in Saltstack & Ansible.

In a S-expression-based configuration language, one would either embed an S-expression-based programming language, or generate the S-expressions with a programming language which can manipulate S-expressions.

I don't think that it's that easy to get away from needing Turing-completeness in general. No reason you can't still support rollbacks, dependencies and diffs anyway.