One thing I think would benefit Emacs Lisp as a language a lot would be
a standard library cleanup. An effort to go through the libraries that
come with Emacs, separate them into "standard library" and "extensions
that come with Emacs", and then go through the "standard library",
provide sane names when necessary (like setcar is provided for rplaca)
and deprecating the old ones, or simply deprecate all but one version of
functions with overlapping use (nth or elt, pick one). Finally, add
standard libraries for common functionality that is currently lacking
(see above).