Windows Cardspace custom Authentication

Question

I would like to add my own authentication mechanism to the Windows CardSpace Client. Currently I see four authentication mechanisms:

1. X.509 certs
2. Kerberos
3. Username/Pass
4. Personal Card

Is there a way to add other authentication mechanism and use some type of handler? This seems weird to me that it is not available. I think I may be able to modify another client that is open source like Higgins selector but I wanted to see if there was a way to use the built-in CardSpace client. I have not been able to find this anywhere.