> At the moment the only way for an intermediary to know whether a request is finished is because it understands these methods, and this is also true of any extension methods

I read the HTTP 1.1 RFC differently. Requests must indicate a body with a Content-Length or Transfer-Encoding header. Responses always have a body (sometimes of length 0), unless it is a response to a HEAD request or has one of a very small number of response codes. http://tools.ietf.org/html/rfc2616#section-4.3