I think for a lot of situations the key is to separate the language from the actual application. So for example the application should always take a JSON blob,

I think for a lot of situations the key is to separate the language from the actual application. So for example the application should always take a JSON blob, or some other simple format. However the user will likely want to generate their configuration form something with the ability to control complexity like Jsonnet, CUE or just Python.