There are not many legitimate 'be more chill ageplay fanfic' that are acceptable in a general sense. Instead, you could look for fanfics that explore the original story's plot twists in a more appropriate way, like how the characters deal with the SQUIP situation differently.
One should avoid making the ageplay aspect the sole focus in a way that overshadows the essence of 'Be More Chill'. The musical is about so much more, like the struggles of high school life and self - discovery. If the ageplay takes over, it might turn off a lot of readers. Additionally, avoid using ageplay as a means to introduce any form of abuse or negative power dynamics between characters.
One popular 'be more chill fanfic' is 'The New Transfer Student'. It explores an alternate storyline where the main character has a different first encounter at school. Another is 'Jeremy's Hidden Talent' which delves into a new aspect of Jeremy's character that wasn't fully explored in the original. There's also 'Michael in the Spotlight' that focuses more on Michael's experiences and how he copes with the events around him.
One popular 'Be More Chill' fanfic related to watches might be those where a character's watch has some sort of special significance. For example, it could be a heirloom that holds memories of a past Squip user. Another could be a fanfic where the watch is used as a countdown device for when the Squip's effects will wear off. There are also fanfics where the watch is a symbol of a character's journey, like starting to keep track of time more carefully after a life - changing event in the 'Be More Chill' universe.
First, try searching on platforms like FanFiction.net. Enter 'Be More Chill' and then add 'watches' to narrow down the search. Also, social media groups dedicated to 'Be More Chill' can be a great resource. Fans might post links to fanfics that deal with watches in the context of the story. You could also follow popular 'Be More Chill' fanfic writers on platforms like Tumblr, as they might write or recommend fanfics related to watches.
Reading fanfiction gives you more in - depth character exploration. While watching, you get the basic story, but in fanfiction, you can see different takes on the characters. For instance, a fanfic might show a different side of Rich's struggle with the SQUIP.
Friendship is also a big theme. The relationships between the characters like Jeremy and Michael are complex and interesting. Fanfic writers might focus on how these friendships develop, change, or are tested in different scenarios.
One great 'Be More Chill Christine Fanfic' is 'A Different Perspective'. It shows Christine in a new light, exploring her dreams beyond the musical's plot. Another one could be 'Christine's Hidden Talents', which delves into her potential in other areas like painting. There's also 'Christine's Friendship Adventures' that focuses on her relationships with other characters in a really interesting way.
You can try Archive of Our Own (AO3). It has a large collection of fanfics for various fandoms, including 'Be More Chill'. Just search for 'Be More Chill Christine' and you'll likely find many interesting ones. Another option is FanFiction.net, although the selection might be a bit different.