I picked up the knuckle-curve when I was about thirteen---and I think Mike Mussina picked his up the same way and for the same reason. I had wanted to try a plain old knuckleball, but I got nowhere with it because I couldn't get the hang of the stiff wrist you're supposed to have; I had a good curve ball that had come attached to my natural sidearm delivery and I threw it with a sharp wrist snap. But I discovered that there is such a pitch as a knuckle-curve, and I experimented with the grip and I picked it up pretty quickly. It became my second-best pitch (my best one, which I learned about three years later, was a good sharp-breaking slider).
So I don't see any problem with learning this pitch. The only real difference is in the grip; you throw it exactly the way you'd throw a curve ball, and it can be a good addition to the repertoire. 8)