RZA needs to move beyond them and play a starring role in one of the films that he scores. He surprised me in American Gangster. Didn't think he could credibly play a cop, but he did.
Of course the Ghost Dog score is one of the most stunning achievements on record in contemporary American cinema. So in one respect you could say, who gives a fuck if the guy never plays any leading roles?
But I think Jarmusch or Tarantino could find the right part for him. Who knows? Maybe they already have.