The Bringers of Oblivion: An alien race that embraces a philosophy of nihilism committed to reducing all matter in the galaxy to a singularity
In sum, the concept is a faction appearing mid-way in a standard campaign, hostile to EVERYthing, that take over some planets (based on scale) and will over time develop a super-weapon to destroy the entire galaxy.
The appeal of this faction, to me, is that it would create a scalable threat to both the player and the AI. The aliens can bide their time, like the player, until they reach critical mass and reveal their true threat to the entire galaxy (a doomsday countdown begins based on scale) and lead to an alternate way to lose the game--Oblivion.
Lore would need to be fleshed out. Lots of possibilities
How this would affect Gameplay:I envision this to be played in conjunction with any other in-game factions such as the Nanocaust without being indistinguishable from them. They would need to pose an ostensive threat to everyone and thus their actions would be noticed by the AI accordingly. Repercussions to follow; AI deals with emerging threat and is thereby exposed to player activities but, if unchecked by humans altogether, then the galaxy is destroyed by the "Bringers of Oblivion." Balance would be tricky but lead to very unique games.
That's all for now,
Would that I was competent in modding or I would do this myself (may be motivated to learn how just because of this game
).