The PiCE will be made from metal, specifically a Zinc alloy using a manufacturing process called die-casting. You'll easily be able to jump on it and you'll probably even drive over it without causing damage to the Pi.
The plastic case you're seeing is a 3D printed prototype, not the finished PiCE.
This one is a little complicated. While the PiCE isn't able to contain batteries at the moment we are designing a set of modules which will fit onto the rear of the PiCE to perform a number of functions. One being to hold batteries so the PiCE can operate away from a power source.