Captain America would also be a key character. His strong moral compass and leadership skills would be important when dealing with the complex ethical issues of time travel. He might be the one to keep the Avengers in line and ensure they don't make any rash decisions that could have disastrous consequences for the timeline.
Tony Stark is a likely focus. His intelligence and experience with technology, especially time - travel technology in the movies, make him a central figure. He could be the one to figure out the mechanics of time travel and lead the Avengers in their time - traveling adventures.
Tony Stark is likely to be a focus. His flamboyant and playboy - like personality could lead to some really interesting scenarios when affected by a love potion. He might make grand gestures towards someone he wouldn't normally be interested in. Another likely character is Natasha Romanoff. Her complex past and guarded nature could create a great contrast when the love potion breaks down her walls.
Loki is another favorite. His mischievous nature means that he could cause all sorts of chaos during time travel. He might try to take advantage of the time - jumping to create his own power base in different timelines or even try to outwit Thanos in ways that the other Avengers can't.
Ant - Man would be a likely candidate as his power already involves size - changing. In fanfiction, his ability could be enhanced or malfunction, leading to all kinds of interesting scenarios. For example, he could accidentally make all the other Avengers the same size as him, creating a whole new dynamic for the team.
Gon would be a likely focus. His determination and simple - minded yet strong - willed nature could lead to some interesting time - travel related stories. He might be on a quest to save someone in the past or prevent a future disaster.
I think Tyrion Lannister would be an interesting character to time travel in a fanfiction. He's very intelligent and cunning. Time travel could be his way to outwit his family and those who have wronged him. Arya Stark could also be a likely character. She has the skills of a faceless man. If she could time travel, she could use her skills to change the past, perhaps by assassinating key enemies before they cause harm. And of course, Melisandre. She has some sort of magic related to seeing the future. It's not a stretch to think she could find a way to time travel in a fanfiction and change the course of events in Westeros.
Captain America would be really interesting. His moral compass and leadership skills in a time - travel scenario would be fascinating. He has to deal with the changes in the past that the time travel causes, and also make sure the other Avengers stay on the right path. He might struggle with seeing his old world again and having to make choices that could change it further.
Sirius Black is a great character to focus on. His rebellious nature can lead to some really interesting time - travel scenarios. For example, he might be the one to break the rules of time travel and cause some chaos.
Hulk (Bruce Banner) could be the focus. Since his body is already in a state of flux between his human and Hulk forms, any changes in his diet or a scientific experiment gone wrong could potentially cause him to gain weight in his human form, which would add an interesting twist to his character.
Batman himself is a likely candidate. Given his intelligence and determination, he might stumble upon a time - traveling device or technology while investigating some strange phenomenon. He would be driven by his need to protect Gotham, perhaps by preventing a future catastrophe that he has foreseen.
I think Fundy would be likely to time travel. He has a complex relationship with his family and the SMP. Time travel could be a means for him to understand his father better or change the way his family relationships developed. GeorgeNotFound could also be a candidate. He's often in the background but has a strong connection to Dream. Time travel might be his way of getting more involved in the SMP's events and helping Dream in a different way. Lastly, Niki could be a time traveler. She has been through a lot of changes on the SMP, and time travel could be her opportunity to go back and make the SMP a more inclusive and friendly place from the start, especially for those who have been marginalized.