IMO, mod_rewrite is a solution for when it's clearly not the application's problem. I've seen unmaintainable messes of rewrite rules and have no wish to encourage that in the apps I support. :-(

Trouble is, this decision is rarely cut-n-dried. I would be trying to push it into the application, even as you're trying for a mod_rewrite solution. All Java frameworks have hooks to hang classes to sort this out, if they can't or won't fix it in the controlllers or actions. Maybe encourage the devs to think of it as a competition. :-)

Wade.