I know that parts of the original design team for YANG are old lisp-fans, but I can't recall the option of developing a lisp-based DSL ever being evaluated. I would personally suggest that the fit would not be very good, since YANG is fundamentally a modeling language that "models the hierarchical organization of data as a tree in which each node has a name, and either a value or a set of child nodes." (https://tools.ietf.org/html/rfc7950#section-4.1).

But I happen to personally think that a datalog- or lisp-based policy language for YANG-modelled data sources would be a very interesting concept.