rlwrap has an option (-f) to preload its completion list from a file. For Clojure, the symbols from clojure.core would seem to be a good choice. The symbols could be generated something like: (doseq [s (keys (ns-publics 'clojure.core))] (prn s))
Completion is as useful to confirm spelling as it is to save keystrokes.
This is an interesting idea, but rather than this, I am planning to investigate integrating Bruce Hauman's rebel-readline which includes completion support.
Not planning to do this