Raising a second Guts out of a wimp like Raki, capable of dispatching Yoma so easily, just by training alone... smells like Hollywood :D Guess if it was even physically possible no one would need the Organization (or at least it wouldn't be so irreplaceable) with their Claymores especially if people fear/dislike them so much -- each town probably would have its own anti-Yoma organization of sorts specially for protecting against Yoma. Judging by the situation we see (a total dependence on Claymores in this matter) it seems like something impossible.
So, we'll see of course, but now I think there's more than just training that makes Raki so strong.