Hm, looks like an old topic but here goes nothing. Different falling rain, possibly light to heavy. And some way to make a waterfall that is more effective then the AoM unit (It restricts too much in your scenario to be effective). Also, Stalagmites, explosions (temporary bursts of fire, useful for a few things, including volcanoes), Cinematic grasses (High ones that are fairly dense and can hide units to a degree), and I'm not sure how you plan to do farms (or the such), but farms with different kinds of crops, orchards/vineyards, and ranch houses. If any of this isn't necessarily possibly, then ok.
