Making Asset Caching and Asset Server work together

While optimizing one of our sites by mixing the Asset Server feature with a CDN, Asset Caching and the Smurf minification plugin I hit an old problem where the asset server feature essentially prevents you from using the asset caching feature.

The problem is described on the original Ruby Trac as bug #10849 here http://dev.rubyonrails.org/ticket/10849 and in Ruby-Forum here Problem with javascript_include_tag with :cache - Rails - Ruby-Forum

We couldn't find any solution so we hacked one together which is described here http://tecnh.com/blog/post/6-speed-up-your-rails-app-with-a-cdn-and-caching

Aside from making this hack recognize the whole cache directory, is there another way of making these features work together? We want static files like app images to be hosted on the Asset server but dynamically generated files like cached assets to be hosted on the App server.