Why She Might Work: Dakota Fanning has been making a gradual transition from Precocious Moppet to Impressive Young Actress, which has given her the ability to simultaneously play fresh-faced and innocent, but also wise-beyond-her years. Rosemary is designed as something of a tabula rasa, which Mia Farrow embodied flawlessly and which Fanning seems capable of doing as well. Plus, as an actress once capable of playing demonic tikes herself, there's some nice symmetry.
Why It's a Bad Idea: Realistically, Fanning is too young, though she's only two years younger than Farrow in the original. Times have changed since 1967 and presenting Rosemary as too much of a child bride would probably confuse the narrative. If NBC held this project for a few years, Fanning would be terrific casting, but if they're shooting in January, the line between "Teen Mom" and "Rosemary's Baby" would get needlessly blurred. Now if *MTV* were doing this remake? Absolutely.