I think, Billi and fantasyfan, you're both right about Henry Crawford. I agree that if Fanny had accepted his attentions early, he would have dumped her, but also that he was sincerely in love with her and that she would have been the means to his redemption, if absence and boredom and vanity hadn't let to his seduction of Maria Rushworth.
Really, I can't forgive Austen for what she did to Henry. He had all sorts of bad traits, but he wasn't stupid. To repeat myself but expand a bit, I can believe he seduced Maria, but I refuse to believe he would have run away with her. The seduction would have been the point for him, and after that, I imagine he quite callously would have told Maria that he had no feelings for her and that if she were wise, in the words of Don Draper, "It will shock you how much this never happened." And while Maria was quite swept away by Henry, I suspect that cold logic and a lack of alternatives would have ruled the day. Much sadder and much wiser, she'd have remained in her marriage. Once she'd licked her wounds, she'd probably have started looking around to see what the other possibilities might present themself while remaining the dutiful Mrs. Rushworth.
As far as Fanny's concerned, a private knowledge, via Julia and Sir Thomas, perhaps, would have been quite sufficient to break off any connection with Henry. But that novel would have been twice as long. I know I'd have loved to have seen Austen give the same treatment to the various actions of the characters in London, as she did during the play rehearsals.