I feel like the issue with designing a setting with the specific goal of of encompassing several different styles or genres of stories is that most authors don't want to write several different genres of fiction. Writers, like most artists, tend to specialize in a particular style, or maybe go through phases from one thing to another as their interests change and evolve over time.

This idea might work as a means for a group of authors to do some sort of interconnected storytelling, like how Marvel brings together magic and space and spy heroes in one story, but that takes a lot of work and planning.