Actually, I've got a good idea for it a little while back. I figured since Starlight Glimmer hasn't really had an album yet, from what I know, it might be a neat idea to do it on her. That, and there are many possibilities for things to "go wrong" per say, with all the time shenanigans. It starts off pretty simple, just an older Twilight telling a story of Starlight Glimmer to a bunch of ponies, after Glimmer and all her friends have moved on. She tells the story of how she grew up with her friend leaving her, and then running away to go find a way to never be hurt like that again. It continues on through the same path that the show stated, albeit with some minor differences. Up until the Season 5 Finale, in which a while after Starlight Glimmer has been all friendshipified, yet still before season 6 (maybe. Still haven't decided on this. Depends on what happens in the 6 Finale), The timelines made with Starswirl's spell begin to converge, as they weren't supposed to exist in the first place. And so, she gets thrown into timeline after timeline, all of which are falling apart and tearing at the seams. She has to find a way to stop whatever force that is altering the timeline (ex. Sombra, Chrysalis, etc.). In doing so, she learns many lessons about teamwork, and friendship, while trying to get to the force and get it/them to stop, or see the light of friendship. It probably wont go through every timeline shown, as that's just too much content for me to write, but It'll go through the main ones, where she learns many lessons about friendship. First she gets sent into the Sombra timeline, where she learns about hatred, and what pain it brings to everypony. Next, Chrysalis, where she learns about Hope, and the choices a leader has to make for the good of their subjects. Then, Nightmare Moon, where she learns about loneliness and separation. Finally, after a brief interlude stating that she did in fact go to the other timelines to shut them down, she ends up at the Wasteland timeline. With no clear force to stop, she's lost. She has to use everything she's learned to find her way back to the main timeline. Weeks, months, maybe even years go by as she trots the wasteland soil, living off of food and water that she barely can scrounge up from the environment. Eventually, after experiencing every single emotion that she fought against in her time in the Wasteland, she realizes that she is the force that she needed to stop. In her crazed state of mind, she fights to think of a way to stop herself. She already knows the joys of friendship, what more could she learn from herself?
And the rest is spoilers for the ending which I have yet to confirm what will happen, but it will likely be bittersweet. How does it sound? Anything I should change before I write too much of the lyrics?