There are fanfictions that focus on the relationship aspect during Tony's palladium poisoning. For example, Pepper might play an even more crucial role. She could be the one to find a solution or at least be the emotional support that helps Tony fight through the physical and mental effects of the poisoning. It shows a different side of their relationship and how they rely on each other in tough times.
Some fanfictions might explore the idea of Tony Stark reaching out to other superheroes for help with the palladium poisoning. He could call on Bruce Banner, for instance. They could work together in a makeshift lab, combining their scientific knowledge. Banner might offer a different perspective on the poisoning since he has his own experience with a body - altering condition, which would make for an interesting read.
One great fanfiction could be where Tony Stark discovers a unique way to counter the palladium poisoning on his own. Maybe he uses his genius to quickly develop a new element, much like in the movies, but this time with a lot more self - discovery and internal struggle. He could have hallucinations due to the poison that lead him to question his life choices and relationships, adding a lot of depth to the story.