Something like a Lisp yeah. I think sub-Turing is interesting for verification/configuration/whatever, but I have a soft spot for small languages with powerful base concepts.
Now you guys made me think of https://github.com/Gabriel439/Haskell-Annah-Library again.
Actually, could you say more about what you have in mind? Something a bit like a config language, maybe -- terminating, sub-Turing -- or something more like a Lisp?