I'm not talking about a mirror, which has a different domain name. I'm talking about a transparent cache like squid. This will mean I don't have to change the O

I'm not talking about a mirror, which has a different domain name. I'm talking about a transparent cache like squid. This will mean I don't have to change the OS images that I might not even control in order to get traffic savings, whereas under your model I would have to, which again, may not even be feasible.