That would be amazing for teaching vim! I've been using vim for a decade and I'm always learning new things about it. A modal keyboard would be incredibly instructive.
It's worth it. Once you grok it, you'll be composing new movements + actions and before long you will be 'thinking in vim'. You also need a very small subset of stuff to begin being useful (actions, moments, modes). After that learn about macros/registers, buffers and windows and you're pretty much good to go.
The video displayed previously had an older timing controller. Here's a video demo of the current TCM on a different display. It's 10Hz, so it will respond to modifier keys and partially update.
