Another option could be a character who was once a villain or a criminal but is given a second chance through the power of chimera summoning. They use this new ability to redeem themselves and fight for a different cause, which would make for a very interesting character arc.
It could be a young genin who has always been interested in spiders and discovers their arachnid summoning ability. Maybe they were orphaned and had to rely on their own wits and new - found power to survive in the ninja world.
It could be Naruto himself. Imagine Naruto with the power to summon kaiju. He would be even more of a force to be reckoned with. His usual knack for making friends could extend to the kaiju he summons, and he could use their power in his never - ending quest to protect the Hidden Leaf Village and bring peace to the ninja world.
It could be a new genin who has always felt different from the other ninja in their class. This character discovers their kitsune summoning ability during a training exercise and then embarks on a journey to master it.
The main character could be a young orphan who discovers they have the power of a summoner. They grow up in the Naruto world but have always felt out of place. One day, they accidentally summon a pony and realize they have a connection to another world. This character would be on a journey to discover their true identity and the full extent of their summoning powers.
One interesting plot idea could be the main character discovering a unique chimera summoning ability that no one has ever seen in the Naruto world. This new power could lead to various adventures and battles.
It could be another summoner who is jealous of the panther summoner's power. This antagonist summons a powerful and dangerous beast, like a giant snake, to constantly challenge the panther summoner and try to steal their power or reputation.
Arya Stark could be an interesting main character as a summoner. She already has a lot of skills like stealth and combat. If she were a summoner, she could summon the spirits of those she has killed to either help her in battles or to gather intelligence. It would be a new twist on her character.
The main antagonist could be one of the village elders. They might see Naruto's fox - summoning abilities as too dangerous and banish him out of fear. Throughout the fanfiction, they could try to prevent Naruto from coming back to the village, fearing that he'll seek revenge or disrupt the power balance they've established.
One possible plot could be that Naruto is somehow transformed into a Chimera Ant. He retains his memories and ninja abilities but now has to deal with the Chimera Ant society. He might try to use his ninja way to change the cruel nature of the Chimera Ants.
Maybe the character initially struggles with the fact that summoning a hydra is seen as an evil or dark art in the Naruto world. As they progress, they try to change the perception of others about hydra summoning by using it for good, like protecting the village from greater threats. This way, they develop not only in their skills but also in their standing within the community.