The Marauders would likely have a very negative reaction to the Dursleys. Sirius, having run away from his own awful family, would not tolerate the Dursleys' treatment of Harry. He'd probably confront them right away.
Well, it could be chaotic. The Marauders are known for their mischief. Sirius might be really offended by the Dursleys' treatment of Harry. James would probably be shocked at how mean they are. And Remus might try to keep the peace but also be appalled at the Dursleys' behavior towards a young wizard.
Obviously, the Marauders which include James Potter, Sirius Black, Remus Lupin, and Peter Pettigrew. And then there are the Evans family members. Most likely Lily Evans, who is quite important as she has her own story arc and connection to the Marauders, especially James. There might also be other Evans siblings or family members depending on how the fanfiction is written.
In this fanfiction, it could be that the future has a new Dark Lord. The Marauders are brought forward in time to stop this new threat. They face challenges like understanding the new forms of magic and technology that the future Dark Lord has harnessed. They also have to deal with the fact that the future wizarding world has different social and political structures. They might start by infiltrating the Dark Lord's lair using their Marauder's Map - like skills, but find that the map doesn't work as well in the future, leading to all sorts of interesting and dangerous situations.
The main characters would be the Marauders, which include James Potter, Sirius Black, Remus Lupin, and Peter Pettigrew. And of course, Tonks is also a main character in this fanfiction.
In this fanfiction, perhaps the Marauders would be quite intrigued by Tonks' unique Metamorphmagus ability. They might initially be a bit confused or even amused by how she can change her appearance at will.
Well, it could be a really heartwarming scenario. The marauders might be shocked at first to see how much their grandchildren resemble them or their children. They could share stories of their adventures, passing on their wisdom and perhaps even some magical tricks.
The Marauders meeting Ginny in a fanfiction could lead to all sorts of interesting scenarios. Maybe Ginny is a bit star - struck at first, since the Marauders are sort of legends in the wizarding world. They could exchange stories about Hogwarts. Ginny might tell them about how the school has changed over the years, and the Marauders could regale her with tales of their own school days. It could also be a story about Ginny learning from the Marauders' more unorthodox ways of using magic.
In such a fanfiction, perhaps Ginny might initially be met with the Dursleys' typical rudeness. They could be shocked by her magical abilities which she might accidentally display. For example, if she gets frustrated with their behavior, a magical item she has might react in an unexpected way.
One interesting plotline could be the initial encounter between the Marauders and the Evans family. Maybe there's a bit of confusion or misunderstanding at first, like the Marauders' rowdy behavior clashing with the more subdued Evans household. Another could be the development of friendships or alliances. For example, a Marauder might form a special bond with one of the Evans siblings over a shared interest in magic or a particular Hogwarts subject.