We can win a diplomatic game without a big empire as well. We should be self-building the UN regardless, so there's no need to be the population leader.
It is easy to say that we won't have to be the largest Civ, but if we aren't, we throw away all strategies related to gifting the United Nations Wonder. These strategies are what allow you to have a bunch of large AIs liking you and liking each other (usually they'll like each other more than you) due to factors such as shared religion, while still having all of those AIs voting exclusively for you, as your rival is a hated, small opponent.
With us reliant on the game conditions of having EVERY AI and OURSELVES in a religion, the parameters for a Diplo game are VERY TIGHTLY WOVEN--religious bonuses almost certainly must be on our side, as those bonuses that aren't shared will be negative Diplo modifiers from differing religions. The only surefire way to get large AIs that share your religion to vote for you is for our Civ to be the biggest (population-wise, but that usually comes as a direct result of having the most land area) and to gift the United Nations to a small, hated AI (or wait for said AI to built it themselves, which is pretty unlikely to see happen).
At the time of the vote, I imagine we should have:
* 2 vassals
* 2 or 3 AIs who we are on good enough terms with to vote for us
* 1 or 2 hopefull smaller AIs whose votes we don't need. We should still try to please these but not at the cost of others.
I think that I already spoke to this point, but I want it to be extremely clear: any Vassals that we have need to be "the most-well-liked" in the world, otherwise our relations with other AIs will be dragged down. Since that scenario isn't really going to happen, we can't expect to get votes from both Vassals and non-Vassal AIs. Since we can't get enough Vassals and Land Area ourselves (an assumption, but probably a safe assumption) if we only get into 2 wars, we must go for the ZERO Vassals route. Unless you want to share a sure-fire trick that will get AIs to declare on us that you can consistently reproduce in our games, while still being able to get said AIs back to Pleased or Friendly by turn 300 or so, in which case I'd like to hear it. Absent any such trick that consistently works, we can't rely on getting 3+ Vassals and thus we'll have to stick with 0 Vassals.
Basically I can't see why we would have better relations with AIs in a culture victory than a diplo victory. Diplo we should be focusing entirely on having as good relations as possible with other AIs
With a Diplo game, we have to keep many AIs as Pleased as possible or better yet, as Friendly as possible. With a Cultural game, we would be perfectly okay with several "moderately Pleased AIs." The difference is huge. In the Diplo case, we have to carefully weigh each request to "stop trading with our enemy," while in the Cultural case, we can afford to refuse a couple of "stop trading" and "join the war on our side" requests without being in danger of throwing away our victory condition while still keeping most or all of the AIs sufficiently pleased to not declare war on us. Those few Negative Diplo modifiers make the difference between a victory and a loss for a Diplo game, but they are relatively meaningless in a Cultural game. That's your difference, and it's a big one.
?! I can't imagine a culture victory before the AIs have yet to even research as far as Liberalism. Maybe some are happy to skip it, but they'd certainly be able to reach it by the victory turn. The AIs that skip it are the AIs that probably won't run free religeon anyway.
I strongly encourage you to open up some Cultural games. Look in the XOTM games or the HOF games. Any info that you find, please report in the team thread. One example would be to open up a Cultural Victory game (with a good victory date) and see how many of the AIs have Liberalism. Count how many do and how many don't, as well as the AI-Player relationship with each of them... i.e. make a table like the following:
Game Version (just say Vanilla, Warlords, or BTS), Where it came from (HOF, GOTM AA, WOTM BB, BOTM CC), Player Name, Cultural Victory Turn, Cultural Victory Date, AIs with Liberalism and their relationship with the Player, AIs without Liberalism and their relationship with the Player
Warlords, WOTM BB, GreyCardinal, 3XX, 17XX AD, 3-FrPC, 2-AFu
Fr = Friendly
P = Pleased
C = Cautious
A = Annoyed
Fu = Furrious
It's a bit of work to go and grab this info, but you'd be doing something helpful for the team and you'd be learning more in the process. BTS tech dates don't tend to be that different from Vanilla or Warlords (Aesthetics is only one new tech early on, after all) and we don't have a big pool of games to compare against, so for the Liberalism knowledge, it would be acceptable to check Vanilla and Warlords games, as well. Some XOTM games are relative anomalies (one BOTM game started us with 3 Cities, which made an early Cultural game far easier to achieve than normal), but even in such a case, a detail like which AIs know Liberalism can still be gathered and compared effectively.
Maybe it's just that I play exclusively on higher difficulties, on Cheiften or something I can imagine it's possible. This game is on Emporer though, and I can't see it happening.
AI tech levels are HIGHLY dependent upon the Player's actions.
What exactly are we spending our hammers on in a diplo game? If it's going to be a 'proper' diplomatic victory rather than diplomation, we shouldn't be building a huge war machine. We don't need to build anything at all in a diplo victory other than the UN. The only thing we should need to go to war for is the resources, which is a requirement of any strategy.
Well, Missionaries is one item that Mitchum will definitely opt for building a lot of.
However, I still question the feasibility of winning Diplo if we don't have the largest population in the world and the ability to gift our United Nations city.
I don't think it is worth it to put additional constraints on ourselves, such as trying for a "purist Diplo game" where we do not get any territory from wars--we are already constrained by the religious requirement (all Civs must have a State Religion) as well as the war declaration requirement. As a result, we can't win a Diplo game where we only join wars for Diplo bonus points as easily as we could in a game without these restrictions. Thus, war WILL be a BIG factor in a Diplo game.
Overall, I think diplo is indeed riskier than culture (although both have their risks), but the best game is going to be a diplo game. If we're playing to win rather than safely make our way to the middle, we should aim for Diplomatic.
That's easy to say and if I don't think about the details, I would tend to agree. But the more and more that I look at the details of the constraints and what they mean, the more and more I see that getting that perfect Diplo game will require so much finesse that our team might not be experienced enough to pull it off. I take back my earlier statement and am now thinking that 3rd place will be perfectly achievable from a strong Cultural win, while those that win Diplo will have had a lot of lucky factors on their side that just happened to fit into the approach that they followed.
We can greatly reduce the luck factor by planning out a lot of details and preparing for the worst--what happens if our two best allies want to declare war on each other, for example--but I am not convinced that this team wants to play with the required level of detail needed to succeed at a top Diplo spot. If you want it badly enough, you'll have to work hard for it--perhaps to the point that our turnsets will even be 8-10 turns at a time for the first few turnsets, so that we can better analyze the situation and keep on top of potential problems. Are you honestly willing to play the game that seriously? I would be, but I am not certain that we are all on the same page with the concept of serious, detailed play.