I am a little late to respond to this but Dare has a post that reiterates why web services should not be consumed in an RPC-like manner with tight-coupling to WSDL (even if you haven’t bought into SSDL yet).
A consumer should be able to make the decision to ignore messages it doesn’t understand without some auto deserialization process messing everything up. That is why web service consumers need to work directly with raw messages (XML or the actual SOAP message in this case) and avoid any of the proxy stuff that frameworks try to provide.
Once the consumer receives a message, the consumer can inspect the message and if it is not a message the consumer understands, it can simply discard it.
Keep using proxies at your own risk!