The length of the XCOM 2 story really depends. If you focus just on the main objectives and don't do many extras, you might finish in around 20 hours. But if you like to take your time, do all the side quests, and really immerse yourself in the game, it could take up to 30 hours or more.
One funny Xcom story is when a rookie soldier accidentally fired their weapon inside the base during a drill. Instead of hitting the target, they managed to knock over a stack of important papers, causing chaos as everyone scrambled to pick them up.
The story of XCOM 2 and Long War 2 is not the same. Long War 2 is often considered a mod or expansion that adds new layers and twists to the base XCOM 2 story, but they have separate and distinct core narratives.
One plot idea could be a story where a soldier forms an unexpected bond with a captured Viper. Maybe the Viper shows signs of having a conscience, contrary to what the XCOM team initially thought. This could lead to a series of events where the XCOM team has to decide whether to trust this Viper or not.
The uniqueness of XCOM MLP fanfic lies in the combination of two very different universes. XCOM is a dark, strategic, and often gritty world of fighting off alien invasions, while MLP is bright, colorful, and centered around friendship. When combined, it creates a contrast that can lead to really interesting stories. For example, seeing ponies use XCOM - style tactics is both unexpected and engaging.
One idea could be a story where the XCOM 2 soldiers are transported to the Star Wars universe. They could use their advanced tactics and technology to fight alongside the Rebel Alliance against the Empire. For example, their psionic abilities could be seen as a new form of the Force by some in the Star Wars world.
Start with the big fanfiction platforms. Archive of Our Own (AO3) usually has a wide selection. Just type in 'XCOM 2 Viper' and see what comes up. Some might be lemon - themed, but you can easily skip those if you're not interested.
A 'xcom pregnant viper fanfic' might be a very unique take on the XCOM lore. Since Vipers are often antagonists in the XCOM games, a fanfic about one being pregnant could be quite interesting. It could involve themes such as motherhood in an alien context, the survival of the unborn (if applicable to Vipers), and how this situation affects the power dynamics between the XCOM forces and the Viper's species. It might also explore the cultural or social implications within the Viper society if there is such a concept in the fan - created story. Maybe the pregnant Viper has to seek refuge from the XCOM forces, or perhaps the XCOM tries to use this situation to their advantage in some way.