"I've been taking this approach for granted for months, but no longer recall how unconventional it is."
I don't know whether it's unconventional, but it can be implemented in single-threaded Arc, and I use the name "w/global" where you use "making." If your 'making plays nicely with threads and continuations, then I guess I'd consider it strictly more expressive than Arc, but it's up to you to decide if this expressiveness is helpful.
At one point Clojure supported dynamic binding of module-level variables using (binding ...). For some reason, it looks like they changed this policy so the dynamic binding would only work with variables declared (def ^:dynamic ...). So it looks like Clojure programs now use dynamic scope just as explicitly as Arc programs use Racket parameters, but with a less first-class treatment. I'm not a Clojure expert, so I could be leaving out critical details here.