Woo! Having held onto the theme for nearly 24 hours, I'm happy to report that the GGJ17 theme is Waves.
How do you make a roleplaying game about waves? Well, you don't, really. At least I didn't. As with anything, my product has strayed from its brief. It's now a card game. But, basically everything else is the same. I'm still following 3 of those 6 diversifiers, and I've been following the Accessibility guidelines.