I thought this was going to be some sort of thread discussing whether it was legal to use the anti-lock braking sensors from a car on the robot...they're probably COTS, but do they meet the cost requirements?
As for the
real subject, I've played with that textured ABS stuff for rough mockups, and I wasn't too impressed with it. I'd say polycarbonate (e.g. Lexan) has better machinability and strength. The ABS was lighter, but only by a little bit. And while I'd be confident tapping a (small) hole in 1/8 in polycarbonate, I'm not sure if I'd trust the ABS to hold a thread. If you're looking for an opaque material, PVC isn't bad. It's not quite as nice to work with as polycarbonate, but I'd prefer it over ABS for something like this. Alternatively, high-quality birch plywood gives plastic a run for its money. Spray paint it, and few will know the difference.
Have a look at
MatWeb for material information for plastics and composites.