I was going to wait to post this but since this is a hot topic I thought I might as well.
I've written my own Avatar story. It takes place after Korra and focuses on the new Earthbender Avatar. I've completed Book One and Book Two will be finished this weekend. I'm also having concept art done of the main characters so I hope to post that soon.
Here is the link, I hope you enjoy Avatar: Spirit of Earth
P.S please let me know if any of the links don't work. Thanks.