I just had the craziest idea; What if Celestia had a brother? This is how I see it happening:
During the Grand Galloping Galla, a new villain going by the name "Eclipse" kidnaps Celestia and Luna, leaving the maine 6 to find them. Along the way, they team up with the Elements of Heroism, a group of 6 stallions that are direct parallels to the elements of harmony. These new elements would be Sacrifice, Bravery, Strength, Determination, Selflessness, and Leadership. When they reach the HQ of Eclipse, he turns out to be the royal brother called Orion and was being controlled by a creature known as "The Shaddo". Both elements then must work together to stop The Shaddo and save Orion from a mental breakdown.
Any thoughts? Be sure to let me know if I can improve!