I don't know if this goes against any specs or is too difficult to implement, but it seems to me that this would be a neat feature:
MTOM By Request: - If a request comes in using MTOM, then respond using MTOM. - If a request comes in using text/xml, then respond with test/xml. This way, a single deployed service can support both MTOM-enabled and non-MTOM-enabled clients. Any thoughts? -Chris