Another motive could be power. If there's a villain who wants to gain control over the Valley of Peace, kidnapping Tigress could be a way to weaken the defenses. Since she's one of the strongest fighters, her absence would be a big blow to the protection of the valley.
In some Kung Fu Panda fanfiction, if Tigress is kidnapped, it could be a plot device to show the other characters' growth. For example, Po might have to step up even more in her absence, relying on his own skills and the teachings of Master Shifu. He could also learn to trust his instincts better when trying to rescue her. The Furious Five minus Tigress would also have to work together in new ways, perhaps revealing hidden strengths or weaknesses. This kind of situation can create a lot of tension and character development within the fanfiction world.
In the Kung Fu Panda series, their story is mainly centered around their growth in kung fu and their friendship within the Furious Five. Po is often clumsy but has a big heart, and Tigress is the strong and serious one. They support each other in battles and in training, but not in a romantic way.
One possible fanfiction could be about Baby Tigress' training days. Maybe she was the smallest among the young animals training in the Jade Palace but had the fiercest determination. She could be shown struggling with some of the basic moves at first, like how to properly execute a paw swipe. But with time and the guidance of Master Shifu, she gradually overcomes her difficulties and starts to shine among her peers.
There could be a fanfiction where Po and Tigress go on a special adventure together. Maybe they discover a new martial arts technique that combines Po's unique style with Tigress's strength and precision. They might face a new enemy that challenges their relationship and forces them to work even closer.
A common theme is self - discovery. Since Tigress is a complex character, many fanfictions explore her journey to understand herself better, like her emotions and her place in the world of kung fu.
Another interesting plotline is if Baby Tigress has a vision of a great danger coming to the Valley of Peace. She tries to convince the other young trainees and the masters, but no one believes her at first because she's just a cub. So, she decides to take matters into her own paws and starts to train even harder to prepare for this impending doom. Along the way, she meets an old hermit who gives her some valuable advice and tools to face the danger.
Perhaps Po and Tigress get into an argument about the best way to train the new students at the Jade Palace. Po wants to use his fun and unorthodox methods while Tigress believes in strict discipline. Through this argument, they learn to respect each other's views more and find a middle ground.
In the normal plot, the action is mainly centered around kung fu battles and the training of the Furious Five. But if Tigress is pregnant, the story could explore the relationships within the group in a new light. For example, how they support Tigress during her pregnancy. There could be less focus on combat training and more on things like preparing for the new arrival, like decorating a nursery or finding the right food for Tigress and the baby. It would also bring a softer side to the otherwise action - packed world of Kung Fu Panda.
The villain might be seeking ultimate power. Po was a major obstacle in their path to dominating the Valley of Peace or even the whole world. By eliminating Po, they believe they can break the spirit of the resistance. Another motive could be revenge. Maybe Po had unknowingly wronged the villain in the past, and this was their way of getting even.
One interesting fanfiction could be about Tigress going on a solo adventure outside the Valley of Peace. She might encounter new enemies and have to use her unique kung fu skills in different ways. Maybe she discovers a new form of kung fu that she then brings back to the Furious Five.