A really interesting plot could be that the next - generation ponies start having strange dreams about a parallel Equestria. They decide to embark on a journey to find out if it's real or not. Along the way, they meet all kinds of new characters and learn about the true nature of their own world and the possible existence of other versions of it. This journey tests their courage and loyalty, and also helps them grow closer as friends.
One idea could be about a new generation of ponies facing a mysterious magical threat that the older generations didn't encounter. They have to figure out how to use their unique skills and new friendships to overcome it.
Then there's Sweet Song, an earth pony with an amazing singing voice. She uses her songs to bring hope and cheer to other ponies. In many fanfictions, she's the one who can calm down tense situations with her beautiful melodies, and she also has a big role in bringing the different types of ponies together through her music.
One idea could be that the new generation of liars discovers a long - hidden secret about their parents' time as liars that starts to put them in danger. For example, an old enemy from the past resurfaces, thinking the kids know something valuable.
Maybe the daughters or sons of the original 'A' could be involved in some sort of revenge plot. They might think that the original liars wronged their parents in some way and decide to make the new generation pay. This would create a lot of tension and drama as the new liars try to figure out who is after them and why.
Perhaps the next - generation fanfiction could explore a world where quirks start to disappear suddenly. The children of the heroes must find a way to either stop this or adapt to a world without quirks. They could look into the origin of quirks and in the process, uncover secrets about the first generation of heroes that were long forgotten. This would force them to reevaluate what it means to be a hero in a changing world.
One idea could be a pony being reborn with memories of a past life in a different pony world. They could use that knowledge to bring about positive changes in Equestria, like finding new ways to solve friendship problems.
One idea could be that the Dazzlings try to reform and join the main group of ponies in Ponyville. They struggle to overcome their past of using dark magic to steal harmony and learn to use their powers for good.
Well, a plot could involve a villain trying to steal all the cupcake recipes in Ponyville. The ponies then have to work together to protect their precious recipes. It could also be about a pony who has lost their sense of taste and has to go on a journey to regain it by trying different cupcakes. Or perhaps there's a mystery surrounding an ancient cupcake recipe that holds a great secret.
Another plot could revolve around a time - travel aspect in the Twilight Next Generation fanfiction. A young character accidentally travels back in time to when their parents first met and starts to interfere. This could lead to all sorts of changes in the timeline and force them to find a way to fix it before they cease to exist in their current form.
One idea could be the next generation facing a new, more powerful enemy that combines the powers of all the previous villains. They'd have to learn from their parents' stories and develop new skills to defeat it.
A plot idea could be that the next generation of Miraculous holders has to team up with some of the old villains' descendants who are now on their side. They have to overcome the prejudice from the public who don't trust them. Together, they work to stop a new evil that is threatening to destroy the balance between the Miraculous powers and the normal world.