Wouldn't using Squid or Apache as a caching reverse proxy be simpler than redesigning your templates to explicity repoint certain URLs to a new webserver (Mathopd, tux, etc)?
You wouldn't have to invoke any TCL code for resources like css, gif, etc. so it should be faster. You also wouldn't have to migrate content into separate /resource folders for the custom code you've already written.
You might have to make sure cache headers work correctly, but you could probably get around that by enabling caching on the basis of the URL extension (gif|css|jpg|etc).
Has anyone tried this?