Charlie could use magic to simply apparate Harry away from the Dursleys' house. It's a quick and efficient way to get Harry out of that horrible situation.
Perhaps Charlie disguises himself as someone the Dursleys trust, like a social worker or something. Then he can easily take Harry with him under the pretense of some official business.
Charlie might bring some of his dragon - taming skills into play. He could create a distraction using his knowledge of magical creatures. For example, he could make it seem like there's a dragon on the loose near the Dursleys' place. While they're all panicking, he grabs Harry and gets away.
Charlie might introduce Harry to the dragon world. Since Charlie works with dragons, this could be an exciting new adventure for Harry. It would also give him a new perspective on the magical world and something to focus on other than his difficult past with the Dursleys.
I'd recommend 'Charlie's Unlikely Alliance'. In this fanfic, Charlie teams up with a group of centaurs to save Harry. Harry has been lured into a trap set by Voldemort in the heart of the Forbidden Forest. Charlie, with the help of the centaurs' knowledge of the forest and their archery skills, manages to outwit Voldemort's minions and rescue Harry. It's unique because it combines different elements of the wizarding world that don't usually interact in the original series.
One great Charlie saves Harry fanfiction could be 'The Rescue by the Dragon Keeper'. In it, Charlie uses his knowledge of dragons and their lairs to find Harry in a dangerous situation. He bravely battles the perils of the Forbidden Forest, where Harry has been trapped by dark forces. Charlie's dragon - handling skills play a crucial role in getting Harry to safety.
Charlie might be a character who has known Hermione for a long time, maybe through some other connections in the wizarding world. He sees Hermione as someone in need of protection from Ron, whether Ron is acting out of his own accord or is being influenced by external forces. In relation to Ron, he is the one who stands against Ron's actions towards Hermione.
Well, in some fanfictions, Charlie might use his dragon - handling skills to protect Harry. For example, he could train dragons to guard Harry or use his knowledge of magical creatures to fend off threats that are related to dark magic and its associated beasts.
For Harry, the author can show his vulnerability. He's used to being the hero, but now in this new situation, he has to rely on others more. He might be scared at times, but also determined to see this through for the sake of the baby. Charlie, on the other hand, can be developed as a very supportive partner. He might have to learn quickly about taking care of Harry, like making sure he eats well and gets enough rest. He could also be shown as someone who is protective, not just of Harry but also of the new life they are about to bring into the world.
They could be like brothers. Harry has a strong connection with the Weasley family already, and with Bill and Charlie, it could be a natural extension of that. They might look out for each other and support one another in any difficult situation.
Edward could use his mind - reading ability. He reads Charlie's intentions and plans his moves accordingly. If Charlie is about to make a decision that Edward believes will be bad for Bella, he can intervene at the right time. He might also be able to manipulate the situation subtly so that Charlie changes his mind without realizing it.
In this fanfiction scenario, Bellatrix saving Harry from the Dursleys is quite an unexpected twist. It could be that Bellatrix has some ulterior motive. Maybe she wants to use Harry for her own dark purposes against Voldemort. She might see Harry as a valuable pawn in the power struggle within the Death Eater ranks.
They could help Harry by teaching him new spells. Bill might teach him some advanced defensive spells he learned as a curse - breaker. Charlie could show Harry some unique ways to use magic around magical creatures. Hermione would of course be there to ensure Harry studies hard and understands the theory behind the spells.