He could go on a quest to find a lost Valyrian steel sword. This would take him across the Seven Kingdoms, facing various challenges like bandits, wild animals, and rival claimants to the sword. He might also have to solve ancient riddles related to the sword's location.
One possible love interest could be a noble lady from another house. For example, a Stark girl. The contrast between the Dayne's southern charm and the Stark's northern stoicism could create an interesting dynamic.
Ned Stark is often paired with Ashara Dayne. Their connection has always been a topic of much speculation in the 'Game of Thrones' fandom, so it's natural that fanfiction writers explore their relationship further.
The focus on the Dayne's sword, Dawn. In many fanfictions, Dawn is not just a sword but a symbol with great power and a long history that is often explored in detail.
One possible fanfiction could start with Arthur Dayne's son being raised in secret. He discovers his father's legacy through an old sword. He decides to train hard to become as great a swordsman as his father was, facing many challenges along the way.
Another fanfiction idea could revolve around Ashara Dayne's life in Starfall. It could show her daily life, her training with the sword, and her relationships with her family members. It might also explore how the events in the rest of Westeros affect her and her home.
One great 'Game of Thrones Arthur Dayne fanfic' is 'The Legend of Arthur Dayne: Dawn of the Knight'. It delves deep into his backstory, showing his training days at the Citadel. It's really interesting as it gives a different perspective on his character compared to what we see in the show.
There's also a fanfiction called 'House Dayne: The Unsung Heroes'. This one focuses on the Dayne family during the time of the Targaryen rule. It gives a lot of details about their relationships with other houses and how they maintained their honor and power. It's really interesting to see how they interacted with the political landscape of Westeros back then.
Margaery can also be a symbol of hope or change in fanfictions with a male OC. If the male OC is disillusioned with the current state of Westeros, Margaery could represent a new way forward. Her charm and intelligence can inspire the male OC to support her in her plans to reform the kingdom. Their relationship then becomes a driving force for the plot, as they strive to make Westeros a better place while also dealing with their own personal feelings for each other.
I think it could be the blacksmith OC who has a strong moral code. For instance, an OC who refuses to make weapons for evil lords or sells his work only to those who he believes will use it for good. This type of character adds depth to the fanfiction and can be very appealing to readers who like complex and morally upright characters.