FWIW, the distinct proxy business can be solved in one of two ways, depending on how complex your proxy needs are.

First, you can just put ``request.meta["proxy"] = "http://..."`` at any point along the DownloadMiddleware before the request is actually transmitted.

Second, you could also just package up that "more control over requests" you described and make it a DownloadMiddleware. AFAIK, the first one in the chain that returns a populated Response object wins, so you could short-circuit all of the built-in downloading mechanism.