Now that I've got initial discussion out of the way, time to start theorizing about the movie!
Okay, so if I had to pick a theme for the movie, I'd like to see more about the past of Equestria. I want to see the story about Starswirl the Bearded and/or a young Celestia and Luna. Hell, they could tell the full story how C & L rose to power through defeating discord. We know Celestia and Luna personally knew Star Swirl, and that he was older than them. It is however unknown if Star Swirl was alive to see Celestia and Luna defeat Discord, or even his initial rise to power.
Hell if they wanted to make a series out of it, they could go through all the major events they've talked about in Celestia's past. For instance the first movie covers Equestria's early life right after founding, and Celestia and Luna's Rise to power through the discovery of the elements and fighting Discord (perhaps explain the origin of the Tree of Harmony through one of Starswirl's last secret experiments or something). The next movie covers the events that cause the founding of the Crystal Empire and its resulting fall to Sombra before being sealed away. Finally the last would cover Luna's betrayal and banishment, followed by Celestia's life during the thousand years following. The only issue with this plan is that the movies would progressively have darker endings, especially for a kids show. Sure the first movie ends all fine and dandy, but the second movie would end with the villain barely escaping and sealing away thousands of innocents along with their entire city, and in turn one of Equestria's main defense mechanisms, before they could be rescued. Finally the third movie would end with Celestia basically losing as she's forced to seal her sister away and over time the commonfolk don't even believe her sister even existed in the first place anymore
Okay, so if I had to pick a theme for the movie, I'd like to see more about the past of Equestria. I want to see the story about Starswirl the Bearded and/or a young Celestia and Luna. Hell, they could tell the full story how C & L rose to power through defeating discord. We know Celestia and Luna personally knew Star Swirl, and that he was older than them. It is however unknown if Star Swirl was alive to see Celestia and Luna defeat Discord, or even his initial rise to power.
Hell if they wanted to make a series out of it, they could go through all the major events they've talked about in Celestia's past. For instance the first movie covers Equestria's early life right after founding, and Celestia and Luna's Rise to power through the discovery of the elements and fighting Discord (perhaps explain the origin of the Tree of Harmony through one of Starswirl's last secret experiments or something). The next movie covers the events that cause the founding of the Crystal Empire and its resulting fall to Sombra before being sealed away. Finally the last would cover Luna's betrayal and banishment, followed by Celestia's life during the thousand years following. The only issue with this plan is that the movies would progressively have darker endings, especially for a kids show. Sure the first movie ends all fine and dandy, but the second movie would end with the villain barely escaping and sealing away thousands of innocents along with their entire city, and in turn one of Equestria's main defense mechanisms, before they could be rescued. Finally the third movie would end with Celestia basically losing as she's forced to seal her sister away and over time the commonfolk don't even believe her sister even existed in the first place anymore