In Plone 3.3 there’s finally a solution for redirects, or at least there is for most of our use cases
There’s an extra option available in your Site Setup – Types (/@@types-controlpanel) where you can say that when you add a Link to your site, this will automatically redirect instead of just showing the link address.
This is also visible in the ZMI/portal_types where the default view for a link is then set to link_redirect_view instead of link_view.
If you set this option, the short name of your link can then function as a redirect.
So, for our usecase: site/index_en.php should redirect to site/english/, we just add a link named index_en.php and as a url we add the full path to the english folder. When people than surf to yoursite/index_en.php, they will automatically get redirected to the english part of the site.
Note: Remember that this only works when you are logged out. If you have rights to edit the link, of course you have to see it first so you can click Edit to change the address if needed.