I think this discussion is interesting on a theoretical level. However, for those self-identifying as diplomacy purists out there, I want to know: Where is the evidence that people not playing for the win is a huge problem on this site? I've finished several games on this site, not as many as some, but not ONE TIME have I ever received an invitaton to join a "game-long unbreakable alliance," nor were any of my diplomatic suggestions turned down because the opponent said he was in a game-long unbreakable alliance with another player or players. Even if these existed, I doubt people would be so open about it. So in the absence of such evidence, how do you distinguish between an "unbreakable" alliance and a breakable alliance that simply hasn't been broken yet?
I also want to argue against the idea that PPSC is a "newbie variant" and somehow inferior to true diplomacy. I can provide one example where the WTA/PPSC difference might have affected my play: Once I had a two-way draw in a PPSC game where, if it was WTA instead, I would have had additional incentives to either: 1. Stop at a 3 way draw, or 2. Stab my ally and play for the win. Although by happenstance I managed to stay in alliance with my ally for the whole game, I wouldn't classify this two-way draw as the inevitable outcome of a "game-long unbreakable alliance". Geographically and diplomatically, I had compelling reasons for keeping my alliance with him and so did he. I made and broke alliances with other nations throughout 90% of the game, and the WTA/PPSC distinction probably would have not affected the play of this greater part of the game. I still would have had the same incentives to enlarge my nation, secure my position diplomatically, and eliminate as many rivals as possible.
I also want to know: when exactly during a Diplomacy game should I begin thinking about making a solo run? In theory, a solo should be every player's primary objective all the time. But oviously the first year or two is way too early to seriously begin plotting a solo. Depending on the map variant, it could be ten years or more before solo scenarios even enter the realm of possibility. It seems to me that everyone, newbie or veteran, has to focus on survival first.