One plotline could be that Penny is hacked by an enemy and turned into a brainwasher to manipulate her friends in RWBY. This would create a lot of internal conflict as the team tries to figure out what has happened to her.
Perhaps Penny is forced to brainwash others as part of a secret experiment gone wrong. And she has to struggle against her programming while her friends try to rescue her and reverse the brainwashing effects on those she has already affected.
It could also be that an outside force uses Penny's innocent and helpful nature against her, making her believe that brainwashing people is for their own good. This would lead to a complex moral dilemma for the RWBY characters as they deal with a well - intentioned but mis - guided Penny.
One possible place to start looking for such fanfiction is Archive of Our Own (AO3). There are often a variety of unique takes on RWBY characters in fan-created works there.
One possible theme could be self - discovery. As the character is reincarnated as Penny, they have to figure out who they are in this new form. Another theme might be friendship, as they interact with the other characters in the RWBY world as Penny. Also, the theme of adaptation, since they need to adapt to Penny's abilities and the situation she is in.
Well, it could involve the RWBY characters seeing future versions of themselves. Maybe they see how their relationships have evolved or how their combat skills have improved. They might also witness future threats to Remnant and start preparing for them in the present.
Well, a possible plotline could start with Ruby being somehow infected or cursed to become a Grimm. She would then experience a whole new set of emotions and abilities. Maybe she starts to have visions or dreams related to the Grimm's origin or their purpose. As she tries to understand what has happened to her, she might be ostracized by some of her friends who are afraid of her new form. However, a few might believe in her and help her. She could then try to use her new Grimm - like abilities, such as enhanced strength or stealth, to fight against a greater evil that is threatening both the Grimm and the people of Remnant. Along the way, she could learn more about the true nature of the Grimm and find a way to either reverse her condition or fully embrace it in a way that benefits everyone.
Ruby would be an obvious choice. Since they are both friends in the RWBY series, a crossover could explore a deeper bond between them. Maybe they go on a special mission together that takes them to a new and dangerous part of Remnant. Another good character could be Weiss. Their different personalities and fighting styles would create interesting interactions. Weiss' ice powers combined with Penny's technological abilities could make for some cool combat scenes.
Another plotline could involve Adam's relationships at Beacon. He might form an unexpected friendship with a human student who challenges his pre - existing beliefs about humans. This friendship could be a central part of his character development in the fanfiction, as he starts to question his long - held grudges and biases.
In some fanfiction, the plot might revolve around Penny's friends' reactions. Her best friends could be either super supportive or have mixed feelings about the situation. There could also be a plotline where Penny's pregnancy leads to a change in her goals and dreams. For example, she might have to put her college plans on hold. And perhaps there's a story where Penny discovers something special about herself during this pregnancy journey, like a newfound strength or a different perspective on life that she didn't have before.
A possible plotline could be that a new enemy emerges in the RWBY world, a puppet master who starts to take over the minds of the hunters and huntresses. The RWBY team has to figure out how to stop this enemy before everyone they know becomes a puppet under the enemy's control.
One possible plotline could be the RWBY characters making comparisons between their own powers and the ones in Dragon Ball Z. They might be shocked at the extreme power levels in DBZ. Another could be them getting inspired by the training methods in DBZ to improve their own skills.
One possible plotline could be that Ruby is kidnapped by a powerful new enemy. This enemy might be after her silver eyes power and plans to use it for some evil scheme. Another could be that Ruby accidentally gets transported to another dimension during a battle, leaving her team to search for her.