Been rolling this around in my head for a bit, since I woke up this morning.
I see it as similar to "free play", except the point of the game is to play well with others, for as long as possible.
The "record" in the Metaverse could be for the longest successful peace stretch.
Civilizations should also not be devoured by culture, perhaps involving the minors-to-majors-and-back-again idea I mentioned earlier, essentially making "total destruction" of a civilization via culture impossible. Another method, perhaps, is intensifying the culture effect the closer to home-world, so that the inner solar system of a given civilization is completely impossible to take via culture?
Hopefully someone else thinks this idea has merit.