Well, in such a fanfiction, a key plot point could be Ichigo's discovery of his new transcendent powers in the past. Maybe he has to face old enemies with his enhanced abilities. Another point could be how his presence in the past alters the future he came from. For example, his interactions with past characters might change their fates, which in turn could have a butterfly effect on the overall Bleach universe.
Ichigo's character may develop by becoming more confident in his powers. In the past, he has a chance to redo things and learn from his mistakes. He could become more strategic in battles, using his transcendent abilities more effectively.
One possible plot twist could be that Ichigo travels back in time and accidentally changes something that makes him not become a Soul Reaper in the first place. This would completely change his destiny and the future of the Soul Society. Another could be that he travels to a time when an ancient evil was first sealed away, and his presence there somehow weakens the seal, leading to a new threat emerging in his present time.
The story could then develop as Ichigo tries to find a way back home. Along the way, he gets caught up in the politics and battles of the DxD world. He might meet Issei and initially be at odds with him because of their different outlooks on power and combat. But as they face common enemies, they start to work together. Ichigo could also have run - ins with powerful devils like Sirzechs Lucifer, who might be intrigued by his power and want to either recruit him or eliminate him as a potential threat.
One possible plot could involve Ichigo's spiritual energy causing a ruckus in the DxD world. His power might be misinterpreted, and he has to prove that he's not a threat. At the same time, he could learn some unique abilities from the DxD characters, and they from him. For example, the devils in DxD might be interested in Ichigo's zanpakuto and its powers, while Ichigo could gain some knowledge about magic from them.
Well, it could be about Ichigo having some super - transcendent powers that he has to hide in the High School DxD world. Maybe he's a new student there and his powers start to disrupt the normal balance of the supernatural elements in the school.
One common theme is power - up. Since Ichigo is becoming transcendent, it often involves him gaining new and extraordinary powers that set him apart from his normal self in the original series. For example, he might have the ability to manipulate time or space.
The exploration of different timelines is really engaging. In 'godlike ichigo time travel fanfiction', Ichigo may visit a timeline where the Soul Society has fallen. His godlike powers then give him the ability to try and restore it. Also, his interactions with past versions of himself can be really thought - provoking. Does he try to change his past self? Or does he let things be? These are all interesting plot elements.
In RWBY fanfiction, a transcendent Ichigo can bring a whole new dynamic. He could potentially have powers that far exceed the normal capabilities in the RWBY universe. His sword skills, for example, might be on a level that no one in RWBY has ever seen. This could lead to interesting interactions with the RWBY characters, like Ruby being in awe of his combat abilities.
One idea could be Ichigo crossing over into a different anime universe like the Naruto world. He could meet Naruto and they'd team up against a common enemy. Maybe a powerful new threat that combines the powers of Hollows and the Tailed Beasts.
Perhaps in the 'ichigo travels back in time bleach fanfiction', Ichigo travels back to the time when the Soul Society was in a more fragile state. He could use his knowledge from the future to help strengthen the Soul Society against upcoming threats, like Aizen's plans. He might train the younger versions of the Soul Reapers and form new alliances that would change the future battles.