I would like it if the browser's DOM view would highlight changes made by an extension (at least directly; if the user injects JavaScript, it might be easier to just show that JavaScript rather than the changes that that code made to the DOM.) Also, it should log it (although this may create security concerns) so that one could occasionally look over what their extensions are doing.
Similarly, there should be a log for AJAX requests made by the extension directly.
Similarly, there should be a log for AJAX requests made by the extension directly.