Hmm, I was turned-off by the collar/neck piece myself. I don't notice it any more, though, and I haven't converted any of my Wraithguard models.
I like the idea you have, and it's very pheasible to perform. It will be easy enough to cut and position the parts, but I imagine that the model will then look like it has a pencil neck. The collar masks the substantial length of the head with respect to the shoulders, hiding the overhang of the head over the shoulders.