Yuck, thats a tough one.
You could restore the COLOR by using vinyl polisher on the wheel but still, it probably won't match perfectly, it will just be a lot darker and won't fix the roughness you speak of.
You could start wearing gloves
You could also find something to go around it I suppose. I like what Saleen has done with their S7 model in terms of the steering wheel (and pretty much everything else):
Looks like they put a centimeter thick piece of leather around the wheel to avoid wearing and add comfort. Maybe they sell those for Bonnevilles.
Hope this helps :-/