@Indigo: I've also done a competition a lot like that. It was called "First Lego League" and we used the mindstorms 1.0 and a freaked-out graphical programming language to do several tasks on a playing field with lego objects, but without any human intervention; we had to program everything procedurally with hard numbers. We didn't fare very well against the competition because of our dysfunctional team and because we didn't have any rotation sensors and nobody was inventive enough to improvise substitutes.
Your model instantly reminded me of a mars rover, probably because of the legs and flat top somewhat reminsescent of a solar panel. About the chains, pulleys, and gears, I'm still suggesting you go with gears, but that you mentioned chains made me wish I was born at a different time. By the time I got into the Technic sets they didn't use the chains much at all.
I like the idea of a openable hood for easy rebuilding, but looking in there I wonder what kind of speed you'll be getting. Instead of using a worm to 24-tooth crown I'd use a worm to a 16? tooth bevel gear or stick a different type of gear out further with some sort of brace. But I'm not familiar with the kind of mothors they had back then so they might have different speed/torque than the ones I'm used to.