Ok so I'm going to revive this because I'm pretty sure I understand what this guys means more than a modder with an attitude problem. (It's more than half an hour to learn Modbuddy and XML for beginners).
So basically a game where you could load in, have more quests, more single faction orientated interactions to support single civ storylines such as the whole world lumping their resources together to get the hell away from earth before it's atmosphere becomes toxic, meteors destroy the planet, someone farts so bad it could wipe out all life as we know it. But basically a game where you're civilization is challenged but not by other civilizations.
An intelligence system to modify the AI so it would move to a continental point or particular place on each land mass, gather it's strength and then launch an all out assault of frenzied aliens at you like a xeno attack from the movie Aliens. Then the challenge is to hold back the aliens, build outposts and build enough strength to either wipe out all nests, research a way to live in peace on the new planet, exodus to yet another place, return to earth with advanced terraforming tech or something similar, be saved by another alien race.
I mean a lot of idea's could come from Alien and Alien Vs Predator, this is more than obvious to me as it would add a massive single player challenge to face xeno swarms every 10 turns or whatever. Also more quests could be developed and implemented to find ways to destroy, pacify or nullify the aliens via crashed Predator satelites and such.
I think this would be a great idea, but yeah like usual I ain't gots the skills.