Ron could be another important ally. His loyalty and courage would be crucial. He might be the one to act as a decoy sometimes, drawing attention away from Harry when he is on a dangerous spying mission. Also, Ron's ability to blend in with the wizarding crowd could help Harry gather information without being too conspicuous.
Dumbledore, even if he's passed away, could still be an ally through his memories or portraits. His wisdom and knowledge of Voldemort would guide Harry in his spying efforts. And there could be other unexpected allies, like some of the centaurs or house - elves who have their own reasons to oppose Voldemort and are willing to help Harry in his dangerous mission.
One possible plotline could be Harry using his unique access to Hogwarts to pass false information to Voldemort's followers. For example, he might tell them that a powerful magical artifact is hidden in a certain place, leading them on a wild goose chase while the Order of Phoenix prepares for a real battle.
Hermione could be one of his allies. Despite her usually rule - following nature, she might side with Harry if she sees the merit in his rebellion. Also, Ron would likely be there, as he has always been by Harry's side through thick and thin.
There are many ways this could happen in fanfic. One way is that Harry uses his connection with Voldemort's mind. Since Harry has a link to Voldemort's thoughts, he might be able to pick up on Voldemort's doubts about Snape. And then Harry starts to investigate Snape further. He might recall some strange actions of Snape in the past, like his ambiguous loyalty during certain battles or his secret meetings with some unknown figures. Combining all these, Harry eventually realizes that Snape is a spy.
Hermione would be extremely shocked and disappointed. She has always been a firm believer in the fight against Voldemort and would see Harry's alliance as a huge betrayal. She would probably try to talk Harry out of it at first and if that fails, she might start her own investigation to find out what made Harry do this.
Ron could be Harry's ally as well. Despite his sometimes clumsy nature, he's loyal and has his own areas of expertise, like wizard chess which could be metaphorically applied to some strategic decision - making in the Ministry. Additionally, some of the younger, more progressive Ministry employees who are inspired by Harry's heroics could also side with him and be his allies in any changes or projects he undertakes within the Ministry.
Hermione would most likely be one of his top allies. She's smart and well - read in wizarding law, so she could help Harry build his case. Ron would also be there for moral support and to offer his own unique perspective on things.
Yes, there are likely fanfics out there with such a wild and unorthodox concept. Fanfic writers often come up with very creative and out - of - the - box ideas, and this is definitely one of them. It goes completely against the established canon of the Harry Potter series, but that's the beauty of fanfiction. It allows for exploring different 'what - if' scenarios.
There could be. The Harry Potter fandom is huge and diverse, with fans exploring all kinds of creative and sometimes out - of - the - box ideas. So it's not unlikely that someone has written a fanfic with this concept. But it may be a bit of a niche idea within the fandom.
Snape could be in great danger. Voldemort might immediately try to kill him. Snape would have to fight for his life or try to escape. His status among the Death Eaters would be completely ruined, and he'd become a hunted man.
Snape could also be a character in such a fanfic. His complex relationship with both Harry and Voldemort makes him an interesting addition. He might be in a difficult position, having to keep his cover as a double - agent while also trying to find a way to save Harry without revealing his true intentions to Voldemort.