That is one of the issues with c.f. shafts for the time being. I guess it could be done if you're ready to accept the risks and lose the warranty which might be already the case after convertion of the joint. After two hours of testing Revo I did like how it played and it made not so bad pair as for the look too with my full spliced butt where the forearm is african blackwood and the joint is carbon fiber but it would look better with no ring at the joint on the butt (IMO).
So If I ever decide to get the cf.shaft I'll better build the cue butt to match the shaft with forearm wood and joint material to make a good combo with the shaft and with no rings to be in harmony.
One more issue for me ...carbon fiber shaft being black makes it not as neutral looking as oldschool wooden shaft and for somebody who is perfectionist when it comes to design it makes the designing of the cue a little bit more complicated. With a wooden shaft any nice butt you like will look great which is not the case with cf...imo