Yeah that's not a bad idea. If Stealth Rock is in effect you can switch in on it then sub to get health to 50% straight away.
I would replace HP with Grass Knot, it's pretty difficult to get HP exactly how you want it. Remember, you've got to breed for the right nature and ability as well...getting everything together would be a nightmare.
Also, Belly Drum is a pretty good move... I'm trying to find out if Belly Drum will end up maxing its Special Attack because that would be awesome. Like if you use BD, get max Attack, the Daruma Mode switches that to Special Attack? But I don't think Atk/SpAtk are directly switched, only the base stats change so that probably won't work.