Good idea, and instead of restricting it to just one out at a time, we should be able to have all of them out at the same time. That way, every time a 'mon gets sent out, it automatically faints. I think it works because you still need 18 turns to set up, so it won't be too broken.
More hazards is one thing but do they really need to be like sr? An icicle type move that hits whichever side strikes first friend or foe for ice type damage would be nice and relatively reasonable, a fire field that works like a permanent non binding fire spin would be another.