I belive that the first step would be separing the particles, as for now we have the same texture for everithing, with color variants
if we had different particles for different terrains, you could get leaves flying too, as a texture of course. Sometimes it breaks my heart when someone goes out of the road and a big green cloud covers the field
it would be really nice to see a different texture for the grass ie. some grass debriss, pieces of mud, etc... you know
it doesn't seem too hard to do, but I'm no programer, so correct me if I'm wrong.