Here's a good way to play multiplayer that fixes the multiplayer problem of "If I kill you then he wins.".
In one-on-one, (or in one-team vs. one-team), you are always willing to expend your resources (i.e., send your army into deadly danger) if you think it will deplete your opponent's resources more.
But with three or more players, if you send your army to destroy player A's army, then player B is going to mop up both of you.
This encourages too much waiting-and-building-up strategy. I hate that. I want to see some good battlefield action and not just fifty turns of conquering independents and building up your super-tech.
Here's a way to play a 5-player game that has both plenty of combat and also interesting diplomacy:
For scoring purposes, arrange the players into a pentagram:
Alice Bob
Charles Doug
Eliza
That's some crappy ASCII art but hopefully you get the idea.
Now the scoring rule is simple: you win when both of the people opposite you are dead.
That's it!
Now what about the people next to you on the pentagram? Well, they aren't your enemies exactly, but they aren't precisely your friends either. It can lead to some very fun diplomacy.
Sometime after I move into my new house (Nov. 1), I'll host a game with these rules. There will only be four slots available, since I'm calling first dibs on one of the five slots. :-)
I'll also use the latest Version of Zen's conceptual balance mod. I like it!