XAdES support in SAML?

An issue came up on the IMI TC call about supporting XAdES
(http://www.w3.org/TR/XAdES/) in the tokens that are transmitted, which
leads naturally to a question as to whether a SAML assertion signature could
use it.

Does anybody have the knowledge and/or time to do a little research and
suggest whether that might be true or not? Specifically, is it non-invasive
enough to fit within the existing XMLSig profile SAML uses?

-- Scott