The thing about "nicotine water" is that, it contains Nicotine. Remember, the PV can be, and is, used without Nicotine.
Without Nicotine in the picture, how can the FDA win the case? Don't make me pull out my "...." scenario.
To me, it's nothing more than an electronic device. Like my monitor.
Maybe PV's could gain common carrier status in the same way ISP's are not held liable for their users actions on the internet