Naruto's ninjutsu and Tonks' magic could create some really cool combinations. For instance, Naruto could use his Rasengan while Tonks uses her magic to enhance its power. Or Tonks could change into Naruto to distract enemies while the real Naruto attacks from a different angle.
One interesting plot could be that Naruto, through some magical accident, ends up in the world of Harry Potter where he meets Tonks. Naruto's unique abilities like his shadow clones could be used in creative ways to help Tonks in her Auror duties. For example, he could send out clones to scout for dark wizards while she uses her metamorphmagus skills to infiltrate their hideouts.
Yes, there are. You can find some on popular fanfiction websites. Some might explore unique relationships between Naruto and Tonks, imagining how their different worlds and abilities could interact in interesting ways.
Well, it's mainly the contrast between their abilities. Naruto has his chakra - based powers like Rasengan, and Tonks can change her appearance at will. Writers can come up with really cool scenarios where they use these powers in unison or in opposition. Also, their personalities are quite different. Naruto is often very determined and energetic, while Tonks is more laid - back in a way. Seeing how they interact and influence each other in fanfiction is really interesting.
Voldemort could still be the main villain in a different way. Suppose he discovers Tonks' unique connection to Harry and tries to use her as a weapon against him. He could manipulate her mind or put her in dangerous situations to force Harry to make sacrifices or bad decisions.
One idea could be that Tonks gets involved in Harry's search for Horcruxes. Maybe her Metamorphmagus abilities help them in disguising and sneaking into places undetected. For example, she could transform into a Death Eater to infiltrate their meetings and gather information.
One idea could be that Jinx somehow gets transported to the Naruto universe. She might initially be seen as a strange and powerful figure. Naruto, being the curious and friendly type, would approach her. Jinx could then start causing chaos in the Hidden Leaf Village, which Naruto has to deal with while also trying to understand her. And they could gradually form an unlikely friendship as they learn from each other's worlds.
A different approach could be that characters from the Matrix world are brought into the Naruto universe. Trinity could learn some ninja techniques from the Konoha ninja. The Matrix characters would be amazed at the concept of chakra and how it can be used for various powers, like walking on walls or creating fireballs.
A major theme is teamwork. In crossovers like Naruto x One Piece, Naruto has to work with the Straw Hat Pirates. They both value friendship and loyalty, but they have different ways of achieving their goals. Also, identity is a theme. When Naruto crosses into the DC Universe, he has to figure out how his ninja identity fits in with the superheroes and villains there. He may struggle with being an outsider at first.
Perhaps the One Ring could have an unexpected reaction to Naruto's chakra. It could either be attracted to it or repelled. This could create an interesting plot where Naruto has to deal with the power of the Ring while also trying to find a way back to his own world.