Taylor Swift to the best of my knowledge has no interest in a acting career, a guest spot wouldn't be out of the question though.
Summer Glau would make a fine choice to play one of main characters, should be within the price range, she would bring a good number of non-trek sci-fi fans to the early episodes.
Kristin Kreuk and Allison Mack ... not sure who they are.
Charlize Theron would be too expensive.
They were both in the Smallville
tv series about young Superman/Clark Kent.