Parmesan is great. It looks and feels so polished that you only realize it's an early version by the lack of certain features.
MSN audio is similar to SIP. There is a service called gtalk2voip that redirects MSN calls to VOIP accounts. I wonder if there is any scope for doing that that in a client. i.e client advertises it is available for chat, and when it receives a request forwards it to a SIP account. And if the chat button is pressed it initiates a call to the sip account and when answered it connects it to the MSN account.