It's a good idea; I would place it more in the "obvious" category than "stroke of genius" but it's clearly got a market.
I think that the technology to do (2) at grid scale is far from ready. The grid was built to distribute power from generating stations out to users. It was not designed to have power flowing into it from thousands of dispersed battery packs at the tips of the network (i.e. residential service points). Significant reengineering and investement will be needed to make this really workable.
Your point is valid, but it's still beneficial to the grid even now to have a bunch of batteries on it: you won't get power flowing into the grid from them, but it does mean output power can be varied a lot more with batteries soaking up some of the difference.
I think that the technology to do (2) at grid scale is far from ready. The grid was built to distribute power from generating stations out to users. It was not designed to have power flowing into it from thousands of dispersed battery packs at the tips of the network (i.e. residential service points). Significant reengineering and investement will be needed to make this really workable.