A cool plot might be that a character discovers a dimension where the Protheans never died out. The story could then explore how they interact with the Protheans and how this new knowledge can be used to prevent the Reaper threat in their own dimension. Also, a dimension where all species are merged into one super - species due to some strange dimensional anomaly could be an interesting setting for a fanfiction.
One idea could be Shepard accidentally getting thrown into a dimension where the Reapers are already victorious. They have to find a way to team up with the remnants of different species to reverse the situation. Another could be a dimension where the Mass Effect fields work differently, leading to unique biotic and tech abilities that Shepard has to learn to use in order to get back home.
A practical answer is Chapter 135, because it turns the idea into a concrete scene. The chapter opens with The sun blazed down mercilessly, but thankfully, the path to the mountain..., adds pressure through At this moment, it seemed more likely to be grim than not., and ends on Are you healed from.
The best chapter pointer here is Chapter 176, "Su Yinwan: I Have a Stronger Taste". It opens with Shang Shaojing didn't suspect anything and popped the greens into his... and closes on Everyone intentionally avoided that plate of ugly-looking but darkly....
If you want the clearest chapter reference, go to Chapter 147. Early on, Xiao Xueyi nodded in agreement after listening.; later, the chapter leans on Su Yinwan seemed to have matured overnight, becoming more and more adept....
A practical answer is Chapter 149, because it turns the idea into a concrete scene. The chapter opens with Seeing that Zhang Cheng's glass was nearly empty, Du Qinglian immediately..., adds pressure through Your only son even resulted from in vitro fertilization., and ends on Zhang, I introduced.
If you want the clearest chapter reference, go to Chapter 138. Early on, Is there such a good deal?; later, the chapter leans on Qi Tianyu quickly nodded in agreement and knelt down to start helping....
The best chapter pointer here is Chapter 147, "Jiang Li, We Are Going to Meet Again". It opens with Xiao Xueyi nodded in agreement after listening. and closes on Only Jiang Li glanced back at Director Sun, and then took out her own....
A practical answer is Chapter 177, because it turns the idea into a concrete scene. The chapter opens with I'm actually the last?!" After the scores were announced, Wen Jiaojiao's..., adds pressure through Next time, stay away from me, I get annoyed just by seeing you., and ends on It was with.
Chapter 175 is the strongest chapter-level answer because it starts from Wen Jiaojiao's eyes nearly rolled back into her head. and follows through on Su Yinwan, who had heard half his words, was a bit puzzled.. The payoff is that the chapter closes with He couldn't say anything;
Chapter 123 is the strongest chapter-level answer because it starts from After He Yun also carefully rolled up her trouser legs and walked down... and follows through on Seeing this, He Yun chuckled softly to himself, then glanced at his own....
A practical answer is Chapter 142, because it turns the idea into a concrete scene. The chapter opens with The ingredients for making Buddha Jumps Over the Wall were still on their..., adds pressure through The unique taste and aroma almost blew his eyebrows away., and ends on Wen Jiaojiao.