There was a lot of interesting trivia at the old version of old TV Tome. I saved it all on my hard drive so I can copy-paste the relevant part here:

Earlier in the season, it was rumored that the entire town of Sunnydale would be sucked into the Hellmouth in the finale. Although it has never been completely confirmed, Joss had another plan for the season. The original idea was to have Anya die in the rubble, Xander be Glory's other half (instead of Ben), Willow was going to become evil after Tara's death and join forces with Glory, and Dawn was to be bled by Evil Willow in the end, and Sunnydale was supposed to be completely destroyed by the Hellmouth.