aid and so horror-stricken by Mrs. Bennet's past prejudice toward Darcy that he must decline permission to marry Elizabeth, a quandary finally overcome by Aunt and Uncle Gardiner.

Or (3) Lady de Bourgh might storm the citadel of Longbourn and completely overwhelm the whole family--except Mary--who then shows her latent worth by citing some homily and putting Mr. and Mrs. Bennet and Lady de Bourgh to shame, thus saving the day.

In all scenarios, I can see no ultimate end other than a happy wedding (skipped over with the briefest of remarks) and a blossoming life for Elizabeth and dear Darcy at Pemberley.

While I can't imagine the novel ending with anything less than the happy ending for Darcy and Elizabeth, a more realistic ending would be a play out of the catastrophic decision of Lydia's running away with Wickham.  Lydia's foolishness jeopardizes the entire family reputation, and if Darcy wasn't the wealthy man he is and hadn't been able to essentially bribe Wickham into actually marrying Lydia, all of the girls prospects for marriage would have been in serious jeopardy.  In modern day money, Darcy paid Wickham hundreds of thousands of dollars to get married.  The purchase of a officer's position in the military would have been extremely costly, and Wickham wasn't otherwise motivated to do the right thing.  He probably regarded Lydia as a foolish girl who was willing to run away to have a good time.  A modern audience would understand Austen's word elope to mean to run away and get married, but Austen's audience would have only understood the word to mean "to run away."  Wickham had already proven that he wasn't interested in marrying a woman of no financial means when he turned his attentions from Elizabeth to Miss King.  He certainly isn't going to change his mind for the charms of Lydia.

If Darcy hadn't saved the Bennet family reputation, he certainly would not have been able to marry Elizabeth and the probably would have continued to caution Bingley from marrying into this family as well.  He would have been a disgrace to their good names.

There could many different endings to Pride and Prejudice.  At the end of the novel, Elizabeth becomes engaged to Mr. Darcy, her true love, despite their differences.  They overcome adversity and their own pride and prejudice to be together.  It's a happy ending.

I don't believe another ending would be appropriate for the novel because in Austen's own life, the love of her life could not be with her.  She lost her happy ending.  He moved to Ireland (her parents did not believe that he could support her sufficiently) and they were never able to marry.  Because she did not get her happy ending, I believe she gave Elizabeth Bennett hers.  Her protagonist is able to "get her man", unlike Austen, who was not.

Possibilities of alternate endings would be Elizabeth and Darcy NOT ending up together and their pride and prejudice getting in their way of true happiness.  Jane and Mr. Bingley could also have not ended up together, either, in an alternate ending, for example.

The answer to this question is difficult, because we have to suspend any knowledge or association with Jane Austen's style of writing, her major themes, and the way that all of her works show her typical "endings" and morals to stories.  Most of Jane Austen's, if not all of them, end happily, with the main female lead ending up with the right guy.  The patient, kind, overlooked females end up with the best men, and are happy.  Silly girls either end up with silly men, or learn to not be silly and value good men for their worth.  Most of her novels, also, have the charismatic, charming guy that turns out to be evil or corrupt or immoral some way, who, in the end, DOESN'T get what they were striving for (usually money, through the means of a woman with an inheritance).  So in order to hypothetically conjecture other possible endings, we have to leave those typical endings of Austen's behind.

There are possible changes to the story.  Maybe Wickham and Lydia don't get married; in other Austen novels, similar shallow females like Lydia have been shunned by their lovers and had to live in dishonor with their ruined reputations.  Wickham could have gone on to marry someone rich--I've always thought it odd that Wickham, such an obviously greedy character, ran away with the poor Lydia at all.  It doesn't really fit; he would have found a wealthy girl to prey upon, and Lydia was not wealthy.  So, I could see Wickham leaving Lyddie and marrying a young girl instead.  I could also see someone other than Mr. Bingley marrying Jane; she was pretty, kind, and Bingley had been convinced she didn't care for him--Jane could have ended up with someone else, and been happy.

However, both of these events--Jane's marriage to Bingley, and Lydia's to Wickham, serve to restore Mr. Darcy in Elizabeth's good favor.  So one has to ask, if Mr. Darcy hadn't coerced Wickham into marrying Lydia (to restore her reputation), and persuaded Bingley that Jane really DID love him, would Elizabeth have changed her opinion of Darcy?  Probably not, and if so, Austen would have had to include other eventualities to tweak her opinion of him.

I hope that these thoughts helped; good luck!