iclaimsidentity and predicate building

I follow microsofts progress on the identity model and have come to understand that there is no perfect setup for the mscorlib claimsidentity. what I do want, is something that I can extend myself yet not have to worry about getting the .net framework 5.0 or 7.5 for that matter, that could contain the next version of IIdentity and IPrincipal and IClaimsIdentity and IClaimsPrincipal. 
That being said, I am curious if there is a methodology that does not depend on yet another dll. I only wish to extend current features that microsoft provides out of the box with the new identity, but allow me to use the core library and not download yet another third party implementation of identity.
Example is, I would provide my application an Interface. Based on that Interface, at runtime, my activator.create would then allow me to use some depencency injection to allow my application to have dynamic authorization mechanisms that rely on the .net framework and make use ...