Wasn't the wide part just supposed to be just some swirling energy around the blade itself. Like for the fire reaver, it would a blade shape at the core and flames emmited from that. For the Material/Spectral Reavers, it would be some sort of ghostly energy and for the elements it would just be emmissions of whatever other element it was imbued with.
I know it's part of the mesh, because you were able to retexture it, but the developers wouldn't have intended the implementation to be taken into account, only the final look. You mentioned that the dark reaver had an extra texture for the core part. That and the hilt are the parts I imagine to behave anything like 'solid'.
"If events are matched closely enough to course, they have a way of restructuring themselves to familiar outcomes." ~ Scorpius, Farscape