Read the description. Starting with KH TWEWY and DR. Lots of Spoilers for these ideas. You've been warned.

What if Lea was too late to save Sora? (Xehanort hits Sora and Sora is now Norted)

What if Byakuya was actually an Ultimate Assassin?

What if Neku was the Conductor after the game ends?

So let's see what you can do. (I'll be updating this book a bit)