I feel like if Versus gets a huge boost in popularity in the Fanfiction scene, Rinri would definitley be at least Top Five most beloved.
He just has that feel about him that would make people go crazy about writing him and any ships involving him.
Certain Natural Enemies surviving losing a fight might also be a popular AU as well, such as with Roya Roach.
In a universe where Shuichi attempted to take down the Mastermind himself, but failed, he entrusts his hopes onto Kaede before getting executed for the murder of Rantaro. Kaede must then go on in an attempt to lead the rest of her class out of their hell.
In my opinion, there are two major candidates to become Kaede's support and one candidate to be her rival.
Supports: Kokichi and Tenko
I imagine that after Shuichi's execution, Kaede would try to attempt to band her classmates together once again. However, despite her efforts, not many people listen to her pleas after it was revealed someone they placed their trusts in killed someone. Even she has her doubts that she could do anything.
This is where the Kokichi and Tenko come in. Kokichi would be the more logical of the two, subtley training Kaede in being a more effective leader while trying to beat into her head that she can't just blindly believe people. He does this so he could lead the students from the shadows while Kaede is in the spotlight.
This comes into practise during the insect meet and greet. When Kaede realizes Kokichi's plan to watch the motive videos, she might agree to watch them, internalizing Chiaki's view from Chapter 3 of DR2, "Belief without doubt is simply a lie." She wants to believe in everyone, but in order for all the players to fully trust each other, everyone has to be on the same playing field, sharing their knowledge.
Tenko would be the more emotional kind of support, ala Kaito. She would try to cheer up Kaede after Shuichi's death, and even offer her lessons in Neo-Aikido to strengthen both her body and her mind. She doesn't quite fully understand why Kaede sides with Kokichi, but decided that she would place her trust Kaede's judgement.
Her rivalry with Angie would be more pronounced than in canon, especially if Angie's actions directly get someone killed.
Rival: Angie
Angie would serve as a foil to Kaede's ideal in uniting everyone. Under Kaede's leadership, everyone has equal say. But under Angie's rule, her underlings blindly follow her every wish in a a belief that she would keep everyone safe, especially after Chapter 2's deaths convincing the initiats of her new Student Council.
In Chapter 3, she could plan out the deaths of the students that she feels are the biggest threats to the safety of the cast, manipulating anyone she deems a fittable sacrifice in order to do so without getting her hands stained black. She might even be willing to commit the second murder herself if the original Blackened couldn't do it, knowing she would be able to get away with it scott-free.
A youtuber who goes by "Ultimate Analysis" recently released a video where he ranked how useful certain characters were during the Class Trials.
I chose to use the list he made where only the top picks of best performing Protagonist, Support, and Rivals got into the Top 16.
Personally, I think the only one who I think could get away with murder in the Top 16 is Nagito. Maybe if he helped Celeste plan his own murder too...
For the Bottom 16... its pure chaos with Toko pointing fingers at anything that moves, Himiko just going with the flow, Taka asking for the killer to reveal themselves, and so much more bs while Kirumi is slowly starting to have a mental breakdown.
Monokuma would be laughing his ass off.