I believe that the developers of Pidgin are considering supporting the Facebook protocol.
I suggest you submit a suggestion to www.Pidgin.im (the web address for the pidgin project), you never know, someone might have beaten you to it.
But I think pidgin is one of those projects, that whilst are great now, its one of those projects that need to die so that linux can move forward (or at least be rewritten).
No AV support, or desire to add it is a pretty big limitation, especially considering MSN messenger has supported it for probably 6 years or longer now. And its no good supporting 30,000 protocols, when all you can do is text messaging. I dunno if its because the code is a nightmare, or if its because no developers are interested though.
So 0. I think its a good idea, I certainly dont think its a bad idea, but we have to be honest about the pidgin project. Its living in the past (along with XMMS).
Windows's default messaging program supports AV perfectly, OSX's ichat support's AV over jabber AND AIM, as well as conference chats. We support, well, just chatting...
Facebook is switching to XMPP (Jabber), so adding support is a waste of time since things are going the other way and Facebook are adding support for Pidgin (along with every other XMPP program, of course, since XMPP is a standard)!
I've been working on this as a 3rd party plugin to Pidgin already. It's a little buggy at this stage, and can only download the buddy list and send messages, but you can grab it from http://code.google.com/p/pidgin-facebookchat/