For APT couldn't you just force HTTP v1 to permit caching?
Most clusters of linux boxes I've admined I end up with a dedicated APT proxy on one machine, not a generic http network level proxy. The proxy I use has varied over time but at this moment I'm mostly using the approx package.
I could; I don't like the idea of multiple versions of a standard being necessary, though. Why can't the newest version support all reasonable use cases?
Most clusters of linux boxes I've admined I end up with a dedicated APT proxy on one machine, not a generic http network level proxy. The proxy I use has varied over time but at this moment I'm mostly using the approx package.