The design of the rover has begun.
This first version of the rover will be a six-wheel drive using a rocker-bogie configuration. The outside four wheels will pivot for spin steering. Each servo will be controlled from the Pi using a 16-channel servo board. I will also use two ESC to control the six motors, one for each side. That leaves ten channels open for future ideas.
One of the design considerations I am thinking about now is keeping the rover body level. One way is with levers on the top of the rover or an internal Counter-rotating Differential. I am going to try the Diff. It will take up some space, but it seems a more elegant solution.
I am still working out which batteries to use.