I support this as long as there is XMPP support as well.
Some servers have the XMPP to AIM, etc transports so you could be killing two birds with one stone, if you found a way to manage it via UI.
It's only one step up from email. Those who use their email address as their msn/yahoo/AIM IM accounts could take part in IM discussions in real time.
This would be cool, but I don't think it's possible - not with the way the peek works.