In this kind of fanfiction, many could support Jon Snow. Bran, with his new powers and knowledge, might see that Jon on the throne is the best for Westeros. Arya could also be a supporter, using her skills to protect Jon and eliminate any threats to his rule. Samwell Tarly, being Jon's friend, would be there to offer his advice and support. And some of the smaller houses that have been oppressed in the past might see Jon as their chance for a better future and thus support his claim to the Iron Throne.
Well, I think Sansa could be one of his supporters. Despite their differences in the past, they are family and she might see the value in having Jon on the Iron Throne. The Mormonts would also be likely to support him. They have respected Jon before and would continue to do so. And of course, Tormund Giantsbane and his wildlings would be there for Jon. They have fought alongside him and trust him completely.
The North would surely support him. They have always seen him as one of their own and a great leader. Also, the wildlings might back him, considering he has a history of working with them and understanding their plight. Davos Seaworth would most likely be on his side as well, given his loyalty to Jon in the past.
Well, in a 'Jon Snow takes the Iron Throne' fanfiction, perhaps Jon discovers some long - lost magic or prophecy that gives him an undeniable claim to the throne. He has to fight off some last - ditch attempts by his enemies to stop him. Once on the throne, he might start a new era of peace by making alliances with former foes. He could also start to rebuild the parts of Westeros that were destroyed during the wars, using the resources and manpower available to him in a smart way.
A great deal of Jon Snow and Iron Throne fanfictions focus on his relationships. For example, his relationship with Daenerys could be very different in fanfictions. In some, they rule together on the Iron Throne, combining their claims and powers. In others, they are at odds, with their relationship being a major obstacle in Jon's path to the throne. And of course, there are fanfictions where his Stark family ties also influence his actions regarding the Iron Throne, as loyalty to his family is a strong part of his character.
Daenerys Targaryen could be one to help. Since she has experience with dragons, she could give Jon Snow advice on how to care for the egg and hatch it.
One ending could be that Jon Snow ascends the Iron Throne alone. He has proven himself as a leader, defeated his enemies, and is seen as the rightful king. This ending might show him ruling with justice and mercy, much like how he was in the original series. Another ending could be that he refuses the throne. After all the chaos and bloodshed, he realizes that power is not what he wants and instead chooses to go back to the Wall or live a simple life in the North.
In a 'Jon Snow sits on the Iron Throne' fanfiction, Jon might start by reforming the way the throne is perceived. Instead of it being a symbol of power and fear, he could make it a symbol of unity. He would have to make tough decisions regarding the remaining White Walkers threats, if any. Also, his relationships with other characters like Daenerys' followers would be very interesting to explore as he tries to bring stability to the Seven Kingdoms.
His half - sister Sansa would likely be one of his allies. She has proven herself to be a shrewd politician and would be a great asset in ruling the Seven Kingdoms. Also, the North would most probably stand by him, considering he is a Stark.
He might meet descendants of the Valyrian people. These could be people who have managed to survive the cataclysm that befell Valyria and have unique knowledge about the place and its history.
Jon Snow could potentially have allies like the Mormonts. They have always been loyal to the Starks. Maybe even some of the Dornish houses might side with him. They have their own reasons to oppose the current power structure in Westeros. And of course, his friends from the Night's Watch who left with him or believe in his cause could be his allies in this conquest. He might also gain the support of some of the maesters who see the value in his leadership for the future of Westeros.
It could be a young and untainted Frey. Maybe a niece or a cousin of the more infamous Freys. One who has not been involved in the past atrocities committed by her family and has a more noble heart.
Daenerys Targaryen is often paired with Jon Snow in such fanfictions. Their combined power and the potential for a different kind of relationship makes it a popular choice among writers. Another character is Arya Stark. Their sibling bond can be explored in new ways when Jon is reincarnated, like Arya helping Jon with her assassin skills in a different plot line.