XMLRPC, GroovyWS with cookies and auth

How do you add cookies or request headers to clients being used for XMLRPC and GroovyWS?
I am currently trying to delegate an existing cookie for a JOSSO secured webapp.

For XMLRPC, I see how I might hack my own version of XMLRPCServerProxy, but it'd be nice if there was some sort of hooks for doing this.  If either I could pass in my own HttpClient (apache) or set of cookies or have a hook to do stuff with the connection before the request is sent, then I could avoid replacing the entire invokeMethod and more.  

Any chance future versions of GroovyXMLRPC would use something like the apache HttpClient instead of URLConnection, so state like cookies could be maintained over a series of requests?

With GroovyWS, I am not sure how to even hack support.  Is there some client somewhere I can get ahold of and add cookies to?

What will these Groovy modules support in the future for authentication?
I hope to get away from JOSSO, but I'll be needed to delegate credentials, like a kerberos ticket.
What methods for credential authentication and non username/password based authentication will be supported?

BTW you should allow username and password to be set per client rather than using system properties as it is in WSClient.    Like that, every service has to use the same account.

thx,

Steve