Seasonal terrains would be an excellent touch.
It could be the same terrains with different textures. Like Spring, Summer, Winter and Fall. We had this in AW but only you saw the terrain you preferred.
You don't\Shouldn't have to remake the terrains, just change textures.
It makes a HUGE difference in immersion and the use of the right skins.
Another idea would be to not only rotate terrains, but rotate terrain seasons, then change the terrain, rotate seasons, change terrain.
This could be done VERY easliy and the pay off for immersion is high.
This would also impact the the skin designs and/or rotating with terrain seasons. It would open up a much wider spectrum for skinners to make seasonal versions of their skins.
This would also impact scenarios.
I think this tiny change would have big impacts on redundacy.
Again, another impact would be the weather itself. There could be snow clouds and snow falling for winter. Pipe dream?
Think about it for a few minutes.
You'd have; Terrain Seasons rotating, skins rotating with seasons and weather rotaing with seasons.
Also re-enable night cycles, because winter snow and moon refelction would make night fighting much easier.
2 cents
~A