What I would really like is mod that mixes magic and technology, like Arcanum (by the way, its an awesome game, the best RPG in my opinion, if you can tolerate its ****ty graphics).
For example, A world where fantasy races coexist (elves, dwarves, orcs along with humans), in which you can wield magic or magic items opposed to technological devices (firearms, mechanical contraptions). Imagine an army of elves with their magic fighting against an army of ironclad dwarves wielding rifles or some sort of technological weapon.
The time setting should be sometime in the second industrial revolution, where you would have a lot of political turmoil between the dying empires and the new emerging republics or nations, and between old fashioned magic users and the supporters of the new emerging technology.
If I find the time and the intelligence (to learn how to mod) perhaps I'll give it a try, although it sound to ambitious for a newbie like me...