Just listened to 100th episode and had to register on forum to respond to the diplomacy comment.
It is an AMAZING game that you absolutely need to play. The flak it gets for destroying friend groups comes from the same section of people who say that about risk (which is a horrible game).
Basically, diplomacy takes a long time, and you're playing against friends, so you'll get tired and annoyed at each other.
First: You guys are roleplayers not people who think that Life is a real boardgame worthy of your attention. You play roleplaying games together for hours on end already. So that length thing won't be that much of an issue (especially if you spread it out over two sessions).
Second: The backstabbing/playing against each other thing also shouldn't be an issue, since you are again roleplayers. If someone attacks Tom (germany) he won't get any more annoyed than he would when Preston died on Luna. When Caleb (england) backstabs Aaron (france) he won't get any more annoyed than any other time that Caleb killed Aaron (sairoc). Basically, your experience killing each other or letting each other die in RPGs will protect you from the issue that crops up in some groups playing diplomacy.
Finally, from hearing your desert island discussion, a game of diplomacy is exactly what you need to play. The world needs to hear how Ross and Caleb outmaneuver each other in total war. It needs to experience Tom in tactical glory. And, most importantly, it needs to experience Aaron playing a Turkish fleet in the North Atlantic.
