Your system could be used to group together static models of a level (houses, static structures , static 3D assets etc ...) I can't imagine the big boost in the games we make if we would have such function to deecrease the draw calls and entities
What's a GEM? As I wrote the framerate raised from 15 fps (4000 small entities) to 500 fps (1 big entity). And you will only get a big boost if you have a lot of low poly model (like grass). For "usual" models this method is useless, there you have to use LOD models.
Btw: to use this method for vegetation is no secret and not new. I just didn't see any useful tool or script on the forums which makes this easy to use/realize.