The premise of the world is unerring diversity. Rather than having 3 - 8 races with rigidly defined abilities and monolithic but intricate backstories, this world has a minimum of 12 races with wild variation inside of each. A lizardfolk could just as easily be a lithe, conniving, underprivileged whiptail wizard as it could a massive, single-minded, shamanistic dragon hierophant.
Perhaps more importantly, the focus will be pulled away from mindless monsters and dehumanized supervillains and set squarely on political and interracial intrigue. The forces of nature have largely been tamed, and most conflict is between people with opposing goals. Macguffins and martial mastery may or may not have their uses, but they're ultimately secondary to detective work, sensitivity to foreign priorities and thought processes, and solid argumentation.
The planned story centers around a frontier town originally founded by an imperialistic kingdom to assert control on the edge of its territory. During the town's growth, it welcomed immigrants from surrounding areas, resulting in a much more diverse, open-minded population than the kingdom typically tolerates. The players will be residents of the town, pooling their various racial and professional talents as they try to guide their town through the process of secession without inciting an unwinnable war with their parent nation.