The proposal (and I've considered it myself, as have others) is to remove the platen glass, so there is no glass between the scanning lens and the film (wet mounting versus dry mounting is orthogonal to the discussion).
Rather than mounting the film where the platen was, the film would need to be positioned at the plane of precise focus, which is pretty much never at the platen. The mechanics are a bit interesting, but I think it is possible. What I don't know is whether the scanning lenses are calibrated to take into account the diffraction (if any) of the platen glass.
Regarding fluid mounting versus dry mounting - with the v700, there is a small improvement, assuming you are also positioning the film in the plane of sharpest focus. But the difference is small, and probably lost if the resulting scan is downsized. On the other hand, I've found wet mounting to be a pretty fast process using betterscanning holders once you get the hang of it, and it deals with flatness very nicely, even with very curled roll film. I don't do it with all scans, but don't mind taking that step for my finest scans.