Well, perhaps in the fanfiction, Ichigo is reincarnated into a modern world where no one believes in the supernatural anymore. He has to find a way to regain his memories and powers while also trying to convince others about the existence of Hollows and Soul Reapers. It could be really interesting to see how he copes with being a 'freak' in a world that doesn't understand.
In an Ichigo reincarnation fanfiction, he could be reincarnated into a parallel universe where the Soul Society is ruled by a different set of laws. He might be reincarnated as a noble in this society and has to use his past experiences to reform the unjust rules. This would involve a lot of political intrigue as well as battles against those who oppose the change.
One idea could be that Ichigo is reincarnated in a different era, like a feudal Japan - style world. He could retain some of his old powers but have to adapt to new forms of spiritual threats. Another idea is that he's reincarnated as a different race, say a Quincy, and has to deal with the internal conflict of his past life as a Soul Reaper.
Maybe fem Ichigo has a different set of powers compared to Ichigo. In the fanfiction, they could train together to combine their powers in a unique way. For example, her powers might be more focused on defense while Ichigo's are on offense, and they learn to complement each other. This could lead to some interesting character development as they overcome their differences and work towards a common goal.
One interesting concept could be how the powers of Naruto and Ichigo blend in the reincarnation. For example, Naruto's chakra control might interact with Ichigo's reiatsu in unique ways. Maybe the Sharingan could have a new form when combined with Ichigo's Hollow powers. Another concept could be the characters' relationships. How would Naruto's friends react to Ichigo's presence? And vice versa, how would Ichigo's allies view Naruto? It could also explore new storylines in the Naruto or Bleach universes that are affected by this reincarnation, like new villains emerging or old ones having different motives.
A crossover with Harry Potter would also be cool. Ichigo could attend Hogwarts as a transfer student. He'd probably be sorted into Gryffindor due to his brave nature. And he could use his Zanpakuto to fight off dark wizards.
An interesting concept could be Ichigo crossing over into a fantasy world and being abandoned in a forest filled with magical creatures. He has to quickly adapt, learn about the new magic system, and fight against the prejudices of the native creatures who see him as an outsider. His journey could involve finding a way back home while also protecting this new world from a hidden threat.
Perhaps in this fanfiction, Ichigo could cross over to a world where zanpakuto are living beings that can freely interact with their owners outside of their sword forms. His relationship with Zangetsu could take on a whole new dynamic as they explore this new world together.
One idea could be that Ichigo discovers he has a hidden connection to the goddess realm. Maybe he is a chosen one to protect the goddess from an ancient evil. For example, he could have special powers that are awakened only in the presence of the goddess.
Well, in an 'ichigo and dc crossover fanfiction', perhaps Ichigo's Hollow powers could be mistaken for some kind of new meta - human ability in the DC universe. The Justice League might initially view him as a threat and try to contain him. But then, when they realize he's there to fight a greater evil, like Darkseid who has somehow tapped into the spiritual energy of Ichigo's world, they join forces. Ichigo could also share his knowledge of the afterlife with characters like Constantine, which could lead to some really interesting storylines.
One idea could be that the baby has a unique power that combines Ichigo's Hollow powers and Rukia's Shinigami abilities. It could be a struggle for them to protect the baby from those who might want to use its power for evil.
A third idea could be a time - travel fanfiction. For example, a character from Highschool DxD travels back in time to the era of Bleach and meets Ichigo when he was still developing his powers. This could lead to some interesting interactions and changes in the timeline of both universes.
One idea could be exploring the inner turmoil of Ichigo as a Hollow in a new and unique way. Maybe his Hollow side starts to have different desires that conflict with his normal self.