Gail and Dewey should have died midway through the movie and Syd's cousin should have killed Sydhey and got away with it only to find out later that Hayden Panettiere's character also lived.And I'm pretty sure that last reason is something the studio disagreed with and why Williamson walked
Then the sequel after 4 could have been Syd's cousin plotting new murders with her main goal being to kill her best friend who screwed up her plan to be the lone survivor of the previous massacre while Hayden tried to figure out who the killer was this time.