Cookie Question

I have read Dave Kristol's "HTTP State Management Mechanism"
document and was wondering if anyone has considered something like a
"Proxy-Cookie"?  It would be analogous to the "WWW-Authenticate"/
"Proxy-Authenticate" requests in that the proxy daemon could request 
that the client set certain state variables when communicating through
a that proxy.  

As a proxy daemon author, I have thought of several potential
features or enhancements that could be made if there was a way
to include more proxy specific data in the request, beyond the
authentication information.   

As it currently stands, a proxy could conceivably send a 
"Set-Cookie" request to a browser, however it would only
be valid for the current domain (at the most) and would
have to be reset every time the client goes to a new domain.

I was wondering if anyone else sees a value in such a 
construct and if it should be pursued further.

--
 Wyllys Ingersoll
 ANS Communications
 Reston VA