What constraints are needed? I've used DSLs that are almost Python but not quite, I think because they were hermetic and deterministic. Even those ended up being produced dynamically using some higher level config DSL or just regular code. Like once you're calling RPCs, it's clearly general programming language territory.
The counterargument is "eventually you'll need every facility provided by a programming language, so just start with a programming language."
I'm not sure how I feel about it. The YAML templating situation in Kubernetes is a [shit show][1]. Then again, I did once cave into the temptation of writing a [lisp-like XML preprocessor][2] to make my configurations less verbose. It doesn't have any access to the environment, though, so it's not a general purpose configuration language, just a shorthand for static XML.
[1]: https://www.davidgoffredo.com/no-string-templates
[2]: https://github.com/dgoffredo/llama