Game
I'd love to see a portion of Prose have a game option. For so many, writing is a calling, but it's also a struggle, and because it's a struggle, it's something many people put off and put off and put off. Tricking your brain into creating great content by thinking about it in terms of a narrative and / or competitive game could jumpstart some truly fascinating and unusual stories. Authors could challenge specific other authors to duels, you could "fight bosses" and "level up" and unlock potions and special skills and badges and titles. Basically finding a way to turn the act of writing a story into a story itself.
It would also be great to have a few shorter, more specific Prose challenges. Rather than just say, "Continue this sentence" and allow it to be fiction, non-fiction, or poetry up to 1000 words, narrow it down. For instance, "Write a logline in 100 words or less ending with 'resulting in the death of the last dinosaur.'" (Etc) It's difficult when a challenge can be open to fiction, non-fiction and poetry because the forms are so different it feels like it's not fair to judge them against each other. Also, by shortening some challenges, it forces you to be far more creative in far fewer words. So yeah, category-specific challenges (and this can include genre-specific challenges), and micro-challenges (100 words or less / 2 sentences or less).
Also maybe a tab to see challenge winners from the beginning of time through the present with links to the challenges they won.