I also have dysmotility/weak peristalsis/weak motility
I have asked this of a few of what I believe are well-regarded GI doctors. Unfortunately, I have not asked it of surgeons.
I think that in general the idea is that it is not an ideal thing to do. HOWEVER, studies seem to show that those with weak peristalsis haven't had any worse post-Nissen outcomes than those without peristalsis.
Regardless, In the words of one of them, "it is not a strong counter-indication for surgery".
If I were in the market for the surgery, I wouldn't worry about my motility being an impediment. In fact, in some people motility actually seems to come back after the surgery.
As a side-note, according to my GI there are a few drugs coming down the pipeline over the next few years that serve to improve motility.