Well, a cool fanfic idea could be that they set some really strict rules at the beginning of their 'friends with benefits' arrangement. Like, no staying over after a night together or no kissing on the lips. But as time goes on, they start to break those rules one by one. This could lead to a lot of interesting drama and internal conflict within the characters as they wonder what it all means.
One idea could be that the two best friends enter into this 'with benefits' relationship secretly, but then they start to develop real romantic feelings. For example, they might find themselves getting jealous when the other is with someone else. Another idea is that they decide to end the benefits part but struggle to go back to just being plain friends because the physical aspect has changed their dynamic so much.
A possible fanfic idea is that the friends with benefits situation starts because of a bet or a dare. Maybe one of their friends dared them to try it out. But then they find that they actually enjoy the closeness more than they expected. However, they also have to deal with the potential fallout in their friend group if others find out.
Chapter 217 is the strongest chapter-level answer because it starts from But Director Sun didn't plan to give her any room to think, he directly... and follows through on Although her initial performance was mediocre, fortunately, Jiang Li....
The best chapter pointer here is Chapter 290, "The Jiang Family is to be Destroyed". It opens with It was nearly evening when Jiang Li checked into Beijing Hospital. and closes on However, just as they were slandering and framing her, Jiang Li's Weibo....
Look to Chapter 269 for the clearest answer. It begins with The next morning, Shen Lan's personal account posted a Weibo., keeps building through [Shen Lan V: Thanks everyone for your concern about our show., and lands on At that time, people guessed it was Shen Lan, and there were even photos....
Look to Chapter 282 for the clearest answer. It begins with The other villagers quickly heard the commotion and hurried over., keeps building through By the time the village chief was alerted and ran over with others, the..., and lands on Why isn't there a live broadcast reporting on their.
Look to Chapter 216 for the clearest answer. It begins with The production team also took advantage of the situation to start an..., keeps building through The enthusiasm has not dwindled over time., and lands on However, the next second, He Yun, who had hardly ever spoken to him,....
If you want the clearest chapter reference, go to Chapter 249. Early on, Jiang Yan's body subconsciously shivered twice.; later, the chapter leans on Jiang, Jiang Li, why have you come back?" Jiang Li's icy gaze shifted away....
A practical answer is Chapter 252, because it turns the idea into a concrete scene. The chapter opens with In fact, Jiang Yan's shirtless appearance this time was entirely Jiang..., adds pressure through They are all sitting in front of the screen watching you now." Jiang Li..., and ends on Aren't.
Chapter 275 is the strongest chapter-level answer because it starts from Hu Zi was exceptionally cooperative, and within half an hour, all the... and follows through on Since you two are considering the village, let's use this money to repair....
A practical answer is Chapter 262, because it turns the idea into a concrete scene. The chapter opens with Wen Jiaojiao couldn't stand it anymore and immediately logged onto her..., adds pressure through Just then, the Southwest Wildlife Protection Association along with the..., and ends on Your.