Really, just make Grass blocks green, like Brick blocks are red. This would make it easier to emulate bushes, trees, or even grass No physical changes even need to be made to the game mechanics . . .
With the way mekorama works, all existing levels would become really ugly, I think having a "leaf" or "bush" block and having it be just a green block with grass texture is way better
How about adding a separate block, the color of which could be decided by the creator? Then the grass block doesn't need to be altered, and we can have a pure green block at the same time.