Thanks for your nice review! We had indeed planned more mechanics.
We'd also thought of the deactivating platform, we envisioned it as a lily pad that would go underwater on every 8th beat. Another idea was to have frogs coming in from the bottom as well, although I also like your idea of differently colored frogs jumping on different beats!
However, on the final day of the jam we didn't progress as fast as we'd hoped, so these additional mechanics unfortunately didn't make it in.