redirects

We have a mercury server setup on VPS.net that is using multi-site to run multiple sites using the same Pressflow install. We recently ran into a problem with implementing our non-www to www canonical domain redirects. In the past we were able to uncomment the section of the .htaccess file included by Drupal to do these redirects because we were not using multi-site. Now that we are using multi-site we have tried to implement the redirects using apache vhosts but the redirect never seems to happen and it appears to be some kind of interference from Varnish that is keeping it from working.

We've got a lot of overlap and duplication of efforts between modules like Path redirect, Global redirect, Secure pages, etc which could potentially really benefit from a unified redirection API and UI. Another advantage is if we can make this redirection API/UI simple, it could be a good candidate to be considered for Drupal 8 Core/CMS.

So...what APIs or features do we need to provide?