Whether or not there will even be intersoverign councils of sorts is unknown and there are many questions as to how they would work and why you'd join them. Regardless, using bidding and/or pooling mechanics would make these councils much more fun. Regardless of whether permenant councils will even get implemented, random events that require bidding and/or pooling with players would be a lot of fun. The goals of which are:
-Provide player interactions we haven't or only rarely see in other 4X's
-Make voting have real consequences that require real backing instead of just clicking yes or no.
-More than just yes/no choices. Middle grounds.
-Increase interactions between factions and give more weight to nation relations (grudges, deception, bickering, politics...)
I'm going to throw out some example events that would call widespread diplomacy of different nations and then explain how to make the options a lot more interesting.
I think someone was eluding to this in the last thread, but basically the idea here is that there is some force or event that is so threatening that it draws all the sovereigns to a council. These would likely be one time gatherings or would only last until the problem is resolved. This twist solves the problem of trying to get people that might thematically kill another race on sight to actually come together without just making separate good and an evil councils.
Example Situation A (Rising Tide)
Sea levels are rising due to some magical event. Obviously this hurts some people more than others so there is immediately reason for some people to care a lot more. Similar situations could include magic all around the world fading and everyone is having a hard time casting. Everyone has casters, but some people will inherently be more magic reliant than others.
These are relatively simple situations where not attending or disagreeing to help solve the problem with other nations would result in a negative relationship hit with the nations who are for the idea.
Example Situation B (Dimensional Invasion)
Portals from another realm have opened at several locations and are spitting forth monster X. Some players might be closers to these gates than others and some players might be better at dispatching the monsters. This one gets more complicated than the previous one since rampaging monsters are a bit more unpredictable than rising sea levels. Because this one is more complicated there might be more possible solutions to it as well.
General Solutions to Situations
In previous games with UN mechanics, voting on global effects were usually a no brainer for most nations. If the basic effect (let's say +10% trade) helped you out more than most people (because you already have lots of trade) you would vote yes without thinking and that was that. I want there to be more politics and more things to consider in an UN mechanics. So I started thing about using a "pooling" mechanic.
Pooling (Global Effect)
It's fairly easy to vote yes and no when you don't have to backup your support for an idea. Let's take the first situation with rising sea levels. Some players might not care since they won't be affected much and they won't even bother to show up. They take a slight diplo hit. The players that do show up will then have to agree on a solution. For simplicity's sake we'll say the only solution to this problem is to assemble 1000 water mana to cast a spell that would stop this.
Each player chooses how much they would like to contribute to the pool in an open fashion where everyone can see how much everyone else is willing to spend and nothing is final until all participants lock their final amounts and then do one final vote to proceed(to combat people attending just to sabotage it, people could be voted out or the remaining players could simply solve the problem without it). If 1000 mana is reached and all participants agree, the spell is cast and the sea doesn't rise. Instead of a simple yay or nay players now have to put their money where their mouth is. There might have been a lot of players who would have gladly voted to stop the flood to help out a friend or just to save a few of their own cities, but you'll see considerably less people actually doing something than just talking.
With this more realistic method players would actually haggle and cut more deals. Watching people try to argue what is fair for each person to donate is pretty hilarious and often results in complete withdrawals and failures to solve the problem, to the peril of most involved. Watching people purposely withholding the last few mana just out of spite is also amusing.
Pooling (Participation Required for Benefit)
For this one we'll use situation B where portals are opening and spewing out monsters. Perhaps one of the options is to cast a similar spell like in the previous situation. Once enough resources are put together the portals all close. There will always be rebels that won't want to help out for whatever reason and for some problems there would be alternative options. Let's say player "A" refuses to help out or even attend despite having a significant amount of portals wrecking havoc in his territory. This problem is still affecting a lot of people, but why should everyone pay when this "A" guy won't lift a finger?
For this situation there are some more options:
-#1 Pool 1000 mana together to remove all portals.
-#2 Pool 1500 mana together to remove only portals near participants.
-#3 Pool 750 mana together to make wards that make portal monsters more likely to attack other players.
Any group of players could decide that they want to solve the problem, but not for everyone. While it may have been more efficient to pay that 1000 mana to get rid of all the portals there will be people who refuse to come to a solution if they know it will benefit certain other players.
Here's an example of how the choices could play out with four groupings of players (who would only see the choices of their group members initially).
[ A ] [ B & C ] [ D & E & F ] [ G & H ]
1 2 3 4
Group 1 is just Player A. Player A is a rebel and says "Screw all this teamwork crap. I'll deal with my own problems" He does not participate at all.
Group 2 is composed of two wealthy players who have enough mana to remove all the portals in the world if they wanted. However they hate player A so much that they decide they will try for a solution that doesn't benefit him. They try for the most expensive solution, #2. Because of how wealthy B & C are the other players demand that they pay even more than their fair share. B & C are enraged that these poor nations would dare to boss them around and they decide that they are so rich that they will just fund the second solution by themselves. Their nearby portals are closed.
The remaining players aren't as wealthy so they decide they want to group together on the less expensive, but less effective option #3. Unfortunately, this group splinters because certain members are sworn enemies from years of war and no deal is able to be made.
Group 3 decides that they still need to deal with the issue even if they can't reach a deal with the other groups. They pick solution #3 and all of Group 3 becomes less likely to be targeted by monsters.
Group 4 is an a similar situation to Group 3 and so they end up choosing solution #3 as well.
[Both Group 3 and 4 have to come up with 750 mana each]
From a relatively simple problem comes so many fun things like strife, compromise, and spite. Was player A right to not participate? That depends on how well of a position he is to defend himself. This whole problem might be just a minor annoyance to him as his army could be simply massive. Perhaps he just doesn't like diplomacy. One interesting thing to take note of in this scenario is that it is a good example of how the punishment for rebel players can increase based upon how many other players besides you chose to deal with the problem. If everyone besides you either had wards or no portals near them you'll probably be getting a larger share of monsters rampaging across your lands.
Another interesting note is how even with incentives to cooperate, players can always find reasons to jerk each other around.
Now imagine how interesting these would get if there were events where players couldn't see how much others were pooling until they already contributed (or not). Lots of bluffing and lying.
Another layer of strategy could be added by being able to openly or secretly pool AGAINST others as well.
Auctions and Bidding Mechanics
Bidding itself is an interesting enough mechanic that there are over a hundred board games based entirely around it. Similar to pooling, but usually with only one group winning. There are several types of bidding mechanisms that can be combined together to create many interesting situations.
Closed vs. Open - In closed bidding, everyone throws out their number and trusts that their number is the highest. In open, players consistently can choose to "one up" the other and bid higher than the leading bids. This is where bidding wars come from.
Winner Take All vs. Proportional - Winner take all is fairly obvious and could easily be modified to take the top X winners. Proportional means that players reap benefits relative to how much they bid (though there could also be bonuses for winning).
Gambling vs. Paying - Standard auctions typically only have players who actually receive something, but there are situations where everyone who bids would lose their offer regardless of whether they receive benefit.
And for some examples:
Example A (Master Artificer)
Open, Winner Take All, Paying
A disheveled figure emerges after a life's work on an amazing artifact, which he offers to sale to the highest bidder at the next global meeting. To spice this up, perhaps there would be alternative options for risky players who choose to try to steal the relic or take it by force, with potentially terrible consequences.
Example B (Death Match)
Closed, WTA/Proportional, Gambling/Paying
A death match is being held and players may send a hero/unit/army to fight for glory, treasure, XP, etc. Winning can be decided by simply the top X participants or by how many other heroes were slain by your champion(s). These fights could also be nonlethal in which case the only thing losers might lose is time or an opportunity.
Example C (The Phantom Castle)
Closed, Winner Take All, Gambling/Paying
Sightings have been seen world wide of a golden castle that appears and disappears periodically. Inside are rumored to be untold treasures. Players would all have the opportunities to assign search parties of varying sizes, but they might have a chance of losing people on the search. Either the player who sent the most troops would find it first and get all the treasure or each troop sent would have X chance of finding it first and reaping the reward.
Example D (It's Raining Gems!)
Closed, Proportional, Paying
Refugees from a volcanic explosion have reported the volcano spewing out rare gemstones all across the land. The race is on to grab as much treasure as possible. Nearby players each choose an amount of troops to send and receive proportional amounts of treasure with bonuses to the highest bidders.
This is a way to take the standard random events like "You have gained 500 gold from...", or "A new resource is found at..." and give players more control over the outcome; it also once again puts players at odds with each other.