I don't think we even need Guile (though I wouldn't complain). Just cleaning up the way packages install (a proper package system, which could be optional) would be a vast improvement for elisp.
By creating a package system, making everything default into the el-user package if not otherwise specified, and moving the core elisp capabilities to the el/emacs-lisp package (used by el-user, importing everything), you'd create a clean path for moving forward. I have zero time and energy to contribute to emacs, but this is really the only fundamental change I'd want as someone who does delve into elisp frequently (or used to, not so much in the past year or so).
By creating a package system, making everything default into the el-user package if not otherwise specified, and moving the core elisp capabilities to the el/emacs-lisp package (used by el-user, importing everything), you'd create a clean path for moving forward. I have zero time and energy to contribute to emacs, but this is really the only fundamental change I'd want as someone who does delve into elisp frequently (or used to, not so much in the past year or so).