>For example, over its lifetime the Clojure community has shifted from accepting argument lists and named parameters in their functions to accepting a single hashmap. This is because the single hashmap is easier to grow over time.

This seems a little nuts, to be honest. It feels like you're just pushing failures from easy-to-diagnose issues with the function signature, to hard-to-diagnose issues with the function body. Basically the function body now has to support any combination of hash parameters that the function has ever taken over its entire history -- Is this information documented? Do you have test coverage for every possible parameter combo?