Quote Originally Posted by Caravel
I'm not sure of the viability of this however, because once you've switched to another faction and ended the turn, the AI will be controlling your faction, and it may do some silly things with your armies...
No, this won't happen. A few members once did a PBM this way (although they didn't get very far). However, you don't have any control over diplomacy. You can make offers, but it's up to the A.I. whether they will be accepted or not.