I have not heard anything Nikki. I would definitely be hesitant putting levamisole in my tank (but I feel the same way about milbemycin), and using it as a dip is obviously not optimal. Because I am out of the hobby for the most part, I don't keep up with these things as often as I would like (not enough time, not enough neurons). As has been the case for the past 20 years, I suspect the hobbiest will solve the problem well before the veterinary medical industry.
The information may be out there, but it would be interesting to see what sort of salinity they can tolerate. If you could lower tank salinity down into the teens (1.019 - 1.015) slowly, that may be too low for these guys. I also wonder if flatworm exit would work, and if there is any residual toxins that one would have to tackle (I am sure that has been tried and a thread is out there describing it).
I will ask around this week to see what I can find out. Even if there is work being done, I don't expect it to be incredibly novel.
As an aside, I find it interesting that most reef publications are labeling it as a "pig dewormer." I am curious where that arose. To my knowledge, it can and is being used in virtually all food animals.