Sorry it took so long for me to get back to looking into this more 
and thus for the long quote above to re-establish context. I have
found that I seem to be able to get eww-auto-rename-buffer 'title,
history titles, and org link capture to work with default readable 
URLs in eww-readable-urls by redefining eww-display-html to:

(defun eww-display-html (charset url &optional document point buffer)
  (let ((source (buffer-substring (point) (point-max))))
    (with-current-buffer buffer
      (plist-put eww-data :source source)))
  (eww-display-document
   (or document
       (eww-document-base url (eww--parse-html-region (point) (point-max) charset)))
   point buffer)
  (and (null document)
       (eww-default-readable-p url)
       (with-current-buffer buffer
         (eww-readable 1))))

This is somewhat less efficient than the prior implementation in that
the document gets displayed twice for default readable URLs, but it is
no worse than not having default readability and manually toggling 
readability after the page is rendered.

I haven't noticed any downsides to this redefinition yet, but I've 
only been playing around with it for a morning so far. Given it 
reduces the conflict between eww-readable-urls and multiple other
features, it seems worth considering.

--- Keith