Despite her fate, I would be Josette. She's my favorite female character, and I would love to play a character set in another time to be able to wear all of those dresses. It doesn't hurt that she's Barnabas' love either.
Kitty Hampshire would've been fun to play, especially if she would've retained her early personality.
Victoria would've been a great character to play on the show in the pre 1795 days, for the reasons Maria stated. But I couldn't handle playing her after 1795, during the Adam storyline and of course there's Jeff Clark. So she's out of the question due to those factors.
Like Maybellique, I wouldn't have minded being a writer. While I watch the show I sometimes think to myself "What if they had done this, instead of doing that?" or "They're passing up a great opportunity here". DS is my favorite show, but I have to admit that if I'd been writing, certain things would've been done differently... : )