The Weasley twins, Fred and George, are also great candidates. We could give them the power of illusion - creation on a grand scale. They can create entire fake landscapes or buildings that are indistinguishable from the real ones for a certain period of time. This would be useful for pranks as well as for strategic purposes in a war - like situation. Professor Snape could have a power of memory - extraction. He can extract the memories of other wizards and witches, not just view them like with the Pensieve, but actually use them to gain knowledge or find out secrets. And Dumbledore could have a power of seeing the potential of a wizard or witch, not just their current abilities.
Hermione would be a great addition. If we're thinking about strange powers, we could give her the power to understand and speak any magical language instantly. It would help her in her research and also in communicating with magical creatures that are usually hard to understand. Ron could have a power of super strength when it comes to handling magical artifacts. He could be the one who can lift the heaviest of enchanted objects without breaking a sweat. Neville could have a power of plant - empathy. He can feel what the magical plants need and communicate with them on a deeper level, which would be useful in Herbology and in battles where plants can be used as allies.
Dumbledore could still play a role, perhaps as a mentor from the shadows. Even though he's no longer alive in the original series, in fanfiction, his wisdom could be passed on through memories or portraits. He might offer cryptic advice to Harry about how to use his new power for the greater good and avoid the temptations that often come with lordship.
Hermione Granger would also be a great addition. She could use her extensive knowledge from the library to help solve problems in the Herbology plot. Maybe she discovers a hidden section in the library about a lost herbology technique and tries to bring it back to the modern - day Hogwarts Herbology class.
Hermione could be one of the main characters. She would be very helpful with all her knowledge of spells and magic theory. She could assist Harry in planning the layout of the village and ensuring that everything is in order.
Hermione Granger would surely be a key character. She is Harry's best friend and is known for her intelligence. She would use her knowledge of magic and laws to try and stop the execution. Ron Weasley would also be important. He would be by Hermione's side, providing his loyalty and bravery. Neville Longbottom could also play a significant role. He has grown into a strong wizard and might lead the resistance within Hogwarts against the Ministry's decision.
Obviously, the Weasley twins themselves are essential. But also including Hermione would be great. She could be the voice of reason when the twins get too carried away with their pranks in the crossover world. Her intelligence and knowledge of magic could help them out of many tricky situations.
Dumbledore could be included. Even though Harry is on his own, Dumbledore's wisdom could still be a guiding force, perhaps through memories or some magical means. Also, Hagrid. His knowledge of the magical creatures could come in handy for Harry in his solo adventures. Another character could be Luna. Her unique perspective might inspire Harry when he's facing difficulties alone.
There could be the typical Sky Gamer characters like experienced gamers who act as mentors to fem Harry Potter in the game world. They might teach her the ropes of Sky Gamer.
There could be Hermione and Ron. Since they are Harry's best friends in the original series, they would likely be important characters in this fanfiction too. They might be curious about Ducky and his relationship with Harry, and could even get involved in some of the adventures that are related to Ducky's past or his influence on Harry.
Hermione could be a main character. She might be initially skeptical about Harry singing muggle music, but then she gets interested in the cultural aspect of it and starts researching the history of the muggle music Harry likes.
There could be an original character who is a descendant of the Uchiha that somehow ends up in the wizarding world. This character could teach fem Harry Potter about the Uchiha ways. Also, Dumbledore could play a role as he always encourages Harry's exploration of different knowledge, and he might be curious about the Uchiha knowledge that Harry is so interested in.