The idea of Moody as a voluntarily enhanced magical cyborg is awesome indeed.

In fact, the entire notion of human enhancement using magic would be an interesting theme to explore. It's already been done to some degree with the idea of defeating death and Harry making a mental note to research mind-altering spells in chapter 12 (intelligence explosion?), but things like Moody's eye and Wormtail's hand (which was strong enough to crush stones) show that there are also ways for Wizards to improve their abilities by replacing body parts with magical counterparts. Seeing what the wizarding world and/or Harry think of such ideas would be pretty interesting.