I thought that I read/heard that in MP games a player could take control of a different faction if his original faction got removed. Is this true, or am I hallucinating this? It certainly wouldn't be my first hallucination!

I have looked through the manual and quickly reviewed the forums and found nothing on this. I'm asking because I am in a 6 person MP game and one of the players is the Belgae...and by Turn 30 he is on the verge of extinction. It would be sad if his game was over, especially this early. Is there anything that we can do?
Thanks,
choppinlt