One idea could be that the peace contract is a magical document created by the Ministry of Magic to end a long - standing feud between two wizarding families. Harry could be involved in ensuring that both families abide by the terms of the contract.
Another possibility is that the peace contract is a very old and powerful magic that has been lost. Harry stumbles upon some clues about it in his research at Hogwarts. He then embarks on a journey to find the rest of the contract and use it to bring peace to the wizarding world which is on the verge of a dark war.
Perhaps the peace contract is related to the magical creatures. Harry discovers that there is a brewing war between different groups of magical creatures and the peace contract is the only hope to stop it. He has to convince the leaders of these groups to sign it.
Perhaps a contract fanfiction where Harry enters into an agreement with the goblins of Gringotts. He might offer his services in exchange for some powerful magical artifacts that could help him in his battle. This could involve a lot of negotiation and interesting lore about the goblin - wizard relations.
One interesting idea could be the complex relationship dynamics that develop due to the marriage contract. For example, Harry might have to navigate new social expectations and deal with characters who have different motives regarding the contract. It could also lead to unexpected alliances or rivalries within the wizarding world.
For a Harry Potter Azkaban contract fanfiction, perhaps there's a contract between a healer and the Ministry of Magic regarding Azkaban. The healer agrees to try and find a way to lessen the effects of the Dementors on the prisoners, but in return, they want access to some restricted magical knowledge. Or it could be a contract between two prisoners in Azkaban. They make a pact to break out together and seek revenge on those who put them there. They might use their combined magical skills and knowledge of the prison's secrets to plan their escape.
Perhaps the contracts having unforeseen consequences. Like the summoner losing a bit of their own magic each time they summon. It adds a layer of risk and drama to the story. In some fanfictions, the summoning contract might be tied to a specific family heirloom, which gives it a historical and mysterious aspect.
In this type of fanfiction, an interesting idea could be the exploration of different Hogwarts houses' reactions to the concubine contract. Gryffindors might oppose it on moral grounds, while Slytherins could see it as a means to gain power or influence. Also, the idea of how the Ministry of Magic would regulate or react to such a contract could be really fascinating.
One idea could be that the marriage contract was made by their families long ago without their knowledge. Harry initially resists but then realizes Cho has some qualities he admires. Another could be that the contract is a magical mistake and they have to work together to figure out how to break it while dealing with their feelings for each other.
One idea could be that the betrothal contract is used as a political tool to unite two wizarding families or factions. This might lead to Harry having to navigate complex political alliances and power plays within the wizarding world.
One idea could be the cultural and family clashes that come with such a contract. Maybe Harry's friends are shocked and have mixed reactions. Another could be how Harry and Tonks grow to understand and care for each other in the context of this contract. For example, they start off as strangers in this arranged - like situation but gradually find common interests.
One idea could be the challenges they face in accepting the betrothal at first. Harry might be hesitant due to his loyalty to his friends and the wizarding world's expectations. Daphne, on the other hand, could be dealing with her family's pressure and her own feelings towards Harry.
One interesting idea could be Naruto using new forms of his jutsu to promote peace. For example, he might develop a jutsu that can heal the emotional wounds of people, thus mending the rifts between warring factions.