Simulate 'grass' using a replicator
I went through all the library replicators and found one that used a Randomize behaviour on the cell's Object.Angle Randomness.Angle Randomness. This looks okay. Everything is still kinda moving in sync if you look carefully but things go to different angles more naturally. I think overlaying a couple of these will look about right for my purposes. But I'd still rather each replicated element had parameters of its own.