Finally, with a lot of help from sgen.exe and a number of very talented inidividuals, I got the complex types to work this morning. The biggest issue was the way WCF compares Strings:
Java does sttring interning, .NET does not do this by default (this is why (object) string1 == (object) string2 is without further consideration a bad idea). Within the XML serialization framework however, WCF uses a NameTable to "atomize" (i.e. intern) strings. The Reader must return interned versions of the name, localName, namespace, etc. or the string comparisons in the generated classes will fail. Here is a sample from the generated code:

while (Reader.NodeType != System.Xml.XmlNodeType.EndElement &&
        Reader.NodeType != System.Xml.XmlNodeType.None) {

    if (Reader.NodeType == System.Xml.XmlNodeType.Element) {
        if (!paramsRead[0] && ((object) Reader.LocalName ==  (object)id4_agedHelloResponse &&
                (object) Reader.NamespaceURI == (object)id2_Item)) {
            o.@agedHelloResponse = Read4_agedHelloResponse(false, true);
            paramsRead[0] = true;
        }
        else {
            UnknownNode((object)o, @":agedHelloResponse");
        }
    }
    else {
        UnknownNode((object)o, @":agedHelloResponse");
    }
}

After fixing the Properties on XmlFiReader, it can now deserialize complex objects, and - as such - also use doc/lit in addition to rpc.