To power the system I'm using a standard 2200mAh 11.1V RC LiPo battery.
A LM2596 circuit provides the 5V for the Pi.
The Pi runs the standard OS Raspbian.
The extandability is given because of the versatility of LEGO.
Via a L293D H-bridge are the motos directly controlled using th GPIO pins.
I'm using the old 9V Lego Technic Motors.