The only FACT established by the script is that within the context of the film other characters are attracted to and seduced by the Sharon Stone character. There is no reason she could not be played by a woman who is not conventionally attractive, as long as the film makes clear that the other characters are attracted to her. It might even be a more interesting film, presenting someone who is less attractive, or obese, or scarred in some way, as the object of desire. If played right, and by talented actors, it might even make the audience more attracted to the character than they would otherwise have been. Would it have a more intellectual audience, one that didn’t come just to ogle the actress? Possibly. Then again, if the less attractive actress revealed her private parts on camera, it might bring in the oglers anyway.