Comment 18 for bug 227733

Ok, I see. I am not sure whether this can be achieved without collateral damage. That means, the idea of mirrors in a mirrors list is to refer to mirrors with identical contents. Handling partial mirrors is complicated because apt has different interpretations of a "404 Not Found" response.

I added an experimental feature once (read: an evil hack) to do such things trying to identify the client ID by connection and judging by the files that it wants to retrieve (search for "keyfile" in the manual). You might try that and report the results, but I cannot promise anything.