The original took me about 14 hours to beat on Normal difficulty, which felt almost too long to be honest.
The only thing I can think would make sense with Wii Motion plus is to use almost only guns where rotation matters, and then giving people full range of rotation for optimal dismemberment. The first game only let you switch between vertical and horizontal.
That idea sounds great on paper, but the hit detection would have to be so amazing I'm not sure it's possible for it to really make a difference.
I mean, can you imagine them programming it so say, a shot to the shoulder joint at 20 degrees is obviously more effective than one at 0 degrees? (0 degrees being perfectly vertical)
I dunno, maybe they could pull it off, but with such a frantic game I have a hard time seeing precision of that level coming into play.
Regardless though, having that amount of control over the angle of the gun will at least feel cool to play.