I initially struggled to think of something thematically that could be considered unexpected, and ultimately unwelcome - especially when considering the sort of technical challenges I wanted to explore. Thankfully, I feel like I ended up with something that does fit, but I do worry about the subtlety of it still.
Regarding your guesswork - you're exactly right. The approach I took to deforming the snow mesh depends on a static piece of geometry to modify vertices of. I couldn't use a higher resolution mesh because my computer was chugging loading it as it was. I couldn't come up with a sensible strategy for dynamically dealing with the snow deformation for procedural terrain. And ultimately, I ran out of time to try alternatives. So, in the end, I just boxed it in to keep players from falling off the mesh.
So glad you enjoyed this little game. And thanks for the feedback!