Shibboleth IDP delegates to another IDP

[Cantor, Scott]

That is not how we intended federation to work. We expect the SP to support the IdPs and "not touching the SP" is an anti-pattern for us, really a non-goal. A good chunk of the world doesn’t believe in that model, but there are no proxying features in the IdP to this point, it's a future item we're working on right now. Even then, our approach won't be as stateful and full-featured as purpose built proxies are, that's just not what we set out to do.
 
-- Scott