I, also, am interested in creating a SearchResponse object from JSON. Our primary interface is a Java service which passes the HTTP response untouched from the ElasticSearch client to a JavaScript front end. For this reason, we cannot use the Java protocols.
However, we also need to connect to this same service from other Java services, as well as write Java integration tests for this service. At present, we are writing two copies of each endpoint, one for each protocol. However, this is increased engineering effort, and prohibits us from using our standard WS-RX Jersey Clients when testing the JSON endpoints, since we have no reliable way of serializing JSON back into Java objects.
I would like to assure you that we do have legitimate reasons for wanting to use HTTP, and would find it incredibly useful if there were a standard method to construct a SearchResponse object from a String of JSON.