Woah, dude. Those are some awesome questions and ideas you show me.
IDEA!
You know that Dragon you talked about, that's as old as Celestia herself? Maybe the princesses have MYSTERIOUSLY disappeared, and the Dragon took over? But the dragon is not a very good ruler, rather an awful one, so Equestria turns to chaos. War breaks out, causing the species of ponies to divide themselves. The dragon's a good guy, so he sends letters to ponies all over Equestria, wanting to bring peace back to the world. But, of course, some ponies do not want Equestria to be united. So they go to his palace and a fight happens. Now the good ponies are on a quest to fight the evil space cats of spacey mountain find the Elements of Harmony to restore peace to Equestria.
I know, it's cheesy.