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.
Power and politics are also common themes. A female Jon Snow would have to navigate the cut - throat world of Westerosi politics. Fanfictions often show her either rising to power, like how Jon Snow did in the original, or facing different challenges because of her gender while trying to gain influence and make a difference in the power struggles.
I'm not sure specifically about 'female Jon Snow lemon fanfics'. Fanfics can vary a great deal in quality and content. However, a lot of fanfic platforms like Archive of Our Own might have some unique takes on a female version of Jon Snow in various storylines, but not necessarily those with 'lemon' content as it often goes against the platform's rules.
Common themes in 'female Jon Snow fanfic' include identity. Since she is a female version of a well - known male character, she has to figure out who she is in this new context. Power and politics are also prevalent. Just like the original Jon Snow, she has to navigate the complex political landscape of Westeros, but with different challenges as a woman. Family also comes into play, especially her connection to the Stark family and how it is affected by her gender change.
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.
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.
Daenerys Targaryen is often paired with Jon Snow in these fanfictions. Their connection in the original series, along with their both being strong leaders, makes for an interesting dynamic. They could rule Westeros together in a new era of peace and prosperity after Jon's rebirth.
The wildlings might be his allies. After all, Jon Snow has had interactions with them before. They are fierce fighters and could fight alongside him against a common enemy.
He could meet ancient Valyrian dragonlords. These dragonlords might still have some connection to their dragons, even if the dragons are long gone or in hiding. Another possibility is meeting the descendants of the original Valyrian slaves who have their own unique stories and skills.