Like many musicians, I enjoy watching live music because it gives me a chance to see how the performers play. For most instruments, this works well -- but keyboard players' hands are generally hidden from the audience by their instrument. Classical pianists usually get around this by facing away from the audience when they play; a few rock keyboardists solve the problem by using a keytar, or a keyboard on a stand tilted away from them.
I'd like to solve this by building a keyboard that doesn't obscure the player's hands: the key mechanism would be designed so that no counterweight would be used at the back of the key, meaning that the keyboard casing could be completely flat at the level of the keys. If a counterweight is necessary, it could be coupled to the key using gears from beneath.
I think it'd be particularly neat if this could be made to work with a real acoustic piano -- but even for a MIDI keyboard, this would allow a weighted keyboard to be built with an unusually minimal appearance.