Another idea for a Star Wars Earth fanfiction is that the Sith somehow find their way to Earth and start causing chaos. A group of brave Earthlings, with the help of some friendly Star Wars characters who also end up on Earth, have to fight against the Sith's evil plans. This could involve battles in famous Earth locations like New York City or the Great Wall of China.
One interesting Star Wars Earth fanfiction could be about a Jedi who secretly lives on Earth and uses his powers to help those in need without revealing his true identity. For example, he might use the Force to stop a natural disaster or prevent a crime in a big city.