I recommend One Piece: The Great God Usopp to you. This book is a story about Usopp. It tells the story of how he obtained the League of Legends system through an accidental transmigration and became invincible. If you want to read a One Piece Doujinshi novel with a deceptive cloth as the main character, this book is perfect for you. I hope you will like my recommendation.
In the past, Usopp's abilities like his slingshot skills might be seen as more primitive compared to the advanced weaponry in his own time. But his creativity could give him an edge. For example, in a time when there were less advanced long - range weapons, his slingshot could be a very unique and effective tool. In the future, if he travels there, his abilities might seem obsolete at first. However, he could adapt by using his knowledge of old - fashioned combat and combine it with the new technology he finds.
Friendship turned to more is a very common theme. Since they start as crewmates with a normal friendship in the original, fanfictions often explore how that can develop into a romantic or deeper emotional bond.
In these fics, Sakura often becomes badass through intense training. She realizes that she needs to be stronger to change things in Konoha or to prove herself. For example, she might train under a mysterious master or in isolation, like in 'Sakura's Solitary Training' where she spends months alone in the forest, honing her skills.
One great Zoro x Usopp fanfiction is 'The Unlikely Bond'. It beautifully explores their friendship evolving into something more. The author does a wonderful job of depicting Zoro's tough exterior softening towards Usopp, and Usopp finding new courage in Zoro's presence.