Interesting. I don't think there've been many games inspired by Nifflas' works, so I'm curious what such a game would be like.
Are the physics going to be closer to WaDF or Knytt Underground? The main difference between them is that the ball physics in Knytt Underground allow for things like bouncing higher than your normal limit by dropping from far enough above. Whereas every ball material in WaDF has a totally fixed maximum bouncing height that can't be exceeded by any means. (Except for the glass ball, but you can only take advantage of that through a glitch.)