I think the main thing is having respect for the mountain of engineering that went into existing solutions and not rolling your own unless you really really have to.
I think an Embedded DSL with post compilation constraint solver based analyzers could take the place of restricted mini-languages while taking advantage of the existing engineering and tooling available for modern languages.
So like a restricted subset? That's a really neat idea; you should develop it into a paper or something.
This restricted subset concept has the huge advantage that you can slip out of the harness in a pinch. So you can reuse a relatively developed Float-less Python program in Full Python and later walk back removing floats.
That's really clever. It essentially obviates the whole configuration DSL tango; it also gets people started where the rubber hits the road -- not with syntax and parsing, but with why the DSL exists and what it's supposed to do and not do.
You can restrict all sort of things, including of course a restricted subset of the language. Such solutions already have headcount at MS which is about as good as it gets for bringing a new thing like this to masses.
When it is released and as it matures we can extend it to do a bunch of other cool things like configuration DSL which would really help clean up Linux. Maybe even build scripts.
You could do stuff like this before with LISP, or Scala compiler plugins. But the tooling and accessibility will make a big difference.
For C# there is Roslyn Analyzers which was a foot in the door for a lot of things. F# has LiveCheck which AFAIK is a lot more powerful. I don't think there is much public info out there; Don Syme demos the use of it to add shape checking for Deep Learning models with full IDE interaction, but any arbitrary constraints can be added and constraint solvers are probably the easiest way to manage and compose those constraints. https://youtu.be/0DNWLorVIh4?t=3410
I think the main thing is having respect for the mountain of engineering that went into existing solutions and not rolling your own unless you really really have to.
I think an Embedded DSL with post compilation constraint solver based analyzers could take the place of restricted mini-languages while taking advantage of the existing engineering and tooling available for modern languages.