I was installing a new Ubuntu 13.10 (daily build) for testing, and came to the option of being able to configure an HTTP proxy server for aptitude. It's been a while since I've sat through an installer and not just cloned a system, and the idea crossed my mind of using our existing HTTP proxy in front of aptitude, to speed up the package update process and reduce bandwidth consumption; however I don't want all of the servers to be incapacitated in the event of a failure on the proxy server, since it is a single point of failure.
I want to configure aptitude to use the existing HTTP proxy, but go around the proxy if it doesn't respond. Any ideas would be great.