[development] custom_url_rewrite_outbound

Hello all, Would it make sense to allow the custom_url_rewrite_outbout to rewrite the base_url, not only the internal path? I have a need to do this with a client of mine and thought I'd throw the idea here to see if it warrants a patch, already done, or if there's another approach to do it. Why I may need this may be a little complicated, but in general, the client has multiple URLs for the same Drupal site, and he wants some of the links to send to the other site rather than internally within the same site. Thanks! AA