I have a planned concept for a mod that seems ridiculous, but that's the point. I want to do a mod that's very humorous, and parodies the series as a whole (though not in a way that sacrifices content or gameplay). It would be called something like "Ultimate Civ Mod," and it would try to incorporate many features from other mods, and throw them back into the main game.
You'd have some of the futuristic stuff from Next War, Final Frontier, and Afterworld, the fantasy stuff from Fall From Heaven, and a load of cool stuff that's original, like new buildings and Civilizations. New civilizations would be added from the realms of fictional continuities all over the place.
It would be a mod where you could feasibly wield a combined army of mages and space marines, as well as see the answer to your questions of whether Dr. Robotnik could beat Sauron. There would be additional turns that allow the building all sorts of crazy new structures like liquor stores, video arcades, pizzerias, and adult novelty shops. Also, an alien invasion scenario is a must.