One idea could be Ulquiorra and Orihime getting sent back to the early days of Soul Society. They could end up changing the course of events that led to certain battles. For example, they might prevent the initial conflict between the Soul Reapers and the Hollows in a way that alters the power dynamics in the Bleach universe.
Another plot could involve them traveling to a time before Ulquiorra was an Arrancar. This would give Orihime a chance to see a different side of him, perhaps a more human side. They could then try to find a way to prevent his transformation into an Arrancar, which would have a huge impact on the future of Hueco Mundo and its relationship with the Soul Society.
A possible plot is that they time - travel to a future where the Soul Society has been completely destroyed. They then have to figure out what led to this disaster and try to change the past to prevent it. Along the way, they might discover secrets about their own powers and the true nature of the Bleach world that they never knew before.
The best chapter pointer here is Chapter 52, "Your Child is in Danger Now". It opens with The village chief and the woman behind him exchanged a glance, "This... and closes on And at this point, they might as well try a desperate remedy for a....
Chapter 882, "Can you still not forget your first love?", is the clearest early answer because it turns Lin Jingshan's situation into a concrete plot event. It opens with Seeing the evidence Lin Jingshan presented, Xu Mei's body trembled...
A practical answer is Chapter 24, because it turns the idea into a concrete scene. The chapter opens with Not only that, even the non-mainstream photos she had previously posted on..., adds pressure through Just because of his arrival, both were severely affected by public..., and ends on Shi Xu.
A practical answer is Chapter 8, because it turns the idea into a concrete scene. The chapter opens with The resentment that had barely calmed among the crowd surged back two..., adds pressure through Why keep harping on the fact that he wasn't a decent man?, and ends on Other people with a.
Chapter 725, "Illegitimate Children Can Also Inherit Property!", is the clearest early answer because it turns Jiang Yan's situation into a concrete plot event. The chapter gives readers a real answer by opening on Jiang Li seemed to have anticipated this answer and squinted, smiling...
Chapter 834, "Where Did This Monster Come From?!", is the clearest early answer because it turns Shang Shuyue's situation into a concrete plot event. The chapter turns that into something concrete by moving from After just a few days on the movie set, Jiang Yan returned home with...
The best chapter pointer here is Chapter 19, "I dare you to touch her!". It opens with What criminal law is this or that, this was originally none of your... and closes on Please give me Miss Su's birthdate." Mr..
If you want the clearest chapter reference, go to Chapter 48. Early on, He Yun felt guilty for initially ignoring Jiang Li on purpose, and with...; later, the chapter leans on That's why he gave her the Perfect Card right off the bat..
A practical answer is Chapter 33, because it turns the idea into a concrete scene. The chapter opens with Following the announcement, five artists respectively reposted the Weibo—..., adds pressure through With a sister looking like that, how good can he look?], and ends on Although Su Yinwan was.
Chapter 858, "If You Dare, Take It", is the clearest early answer because it turns Shuiyun Temple's situation into a concrete plot event.