Stealth Rock could already use a nerf in and of itself. SR needs to be toned down before looking at introducing any other entry hazard to the metagame. A new hazard of any type at this time would, imo, be terrible for the metagame. Spikes and Toxic Spikes are balanced, SR is not. If any new hazard were to be introduced (after current ones were balanced) I would hope that it would act more like (tox)Spikes and alot less like SR. Better rapid spinners would also be necessary before introducing more hazards. We aren't quite at the point where more hazards would be a good idea.