For folks that have never poked around in emacs, the specific difficulty will be that the odds are very high that if you are in an emacs lisp file, you are almost certainly going to want to edit what emacs itself is doing.

I'm specifically talking about scenarios such as "you set debug-on-error."

To that end, the proposal would probably be something like "flymake/flycheck" use a child emacs process to query the code, but the user evaluating the code would still be done in the main emacs?