As a huge diplomacy fan, I'd love to see how this pans out. I mean, super-mega massive diplomatic games are only fun for so long, but your idea with inviting known players is slightly flawed. Playing diplomatic games with people you know sort of ruins it in a way, as I'm sure all of you with diplomatic friends know: you either ally to kill everyone or you fight each other, no matter what.
Right now I am in a rather successful 10 player diplo, the only problem I experienced was the attack on Vietnam for no reason, but other than that it's going along smoothly. Here's the diplo link:https://www.warlight.net/MultiPlayer?GameID=8351173