Honestly, I don't even see the issue. Helena Bonham Carter is a marvelous actress who has played a variety of different roles. Look at just a scattering of her films! Room With A View, Lady Jane, Mary Shelley's Frankenstein, Fight Club, Twelfth Night, Sweeney Todd, Wings of the Dove, Harry Potter, Novocaine etc.
Twenty years ago she'd've been a good choice for Victoria or Carolyn or Angelique. She has that kind of range. Given her current age, she is a good choice of Julia, Elizabeth or Mrs. Johnson.
Sorry, but one thing that bothers me--as an actor myself--is how other actors get pigeon-holed for often-bizarre reasons. James Doohan found his career virtually ruined because no one would believe he didn't speak with a Scots accent. On another board, I read several people dismiss the possible casing of Kate Beckinsale in The Ring (she was under consideration) because it wasn't an action-oriented part (simply dismissing all of Beckinsale's work prior to Underworld and Van Helsing). I vividly recall how loads of people reacted with disgust at Gary Oldman being cast as Dracula, based essentially on his take of Lee Harvey Oswald and Sid Vicious. One of the most chilling human monsters I ever saw on film was in Once Upon A Time In The West. The actor was Henry Fonda.
People, we're talking about ACTORS. If actors are good, they can play all sorts of different parts. Christopher Lee keeps getting cast as the heavy, but I had the great good fortune to see him in Jinnah, wherein he wept with sorry. In his autobiography he noted this was the only chance he'd had to show that kind of emotion in his career. He was superb! Likewise I saw Jonathan Frid on Broadway in Arsenic and Old Lace, essentially playing a brutal, sadistic thug. He was great! Anyone who got to see last weeks' SNL got to view Anne Hathaway doing a truly wonderful take on Mary Poppins--as slightly insane, and fairly promiscuous, mong other things. I for one would love to see her play a villain!
Hmmmm...Anne Hathaway as Angelique....hmmmmmm....
Frankly, it is insulting as well as infuriating to read good actors dismissed in this way. Helena Bonham Carter has the career she has--including all those awards and juicy parts--because she's good. Any DS movie will be lucky to have her, whether Tim Burton directs or not. The only real hestitation I have is that if she plays Julia she might be repeating herself, a la Mrs. Lovett.