It took a long time, but it seems that the time for an older idea of mine has come: Jeff Hodges is reporting on a report he prepared for the MIT Kerberos group to explore the use of SAML tokens in traditional security systems. A while ago, I was exploring a similar idea – then with Eve and Nico – on how to use SAML attribute and bearer token in the context of the GSS-API.
The ideas and concepts we had then would still seem valid to me, although a lot of things have moved on since then. I will definitively follow this, if only from a distance.