[JesseK]

It really depends on where you have to pick up the game piece from, but I have an idea. For easier driver control, you could make the first arm coming off the large bottom sprocket a 4-bar linkage. Adds a bit of weight and slight complexity for mounting the next joint. Yet you essentially add another option in control the driver without having to add sensors, button, or more programming. This wouldn't work if you had to pick something up off the ground, unless you telescoped the arm out (tradeoff in complexity I guess).

At 70 inches long, we really couldn't make a suggest for the reduction until we see a game piece. For instance, this would be perfect for a 2007 tube using dual-FP's on the base, but for the 2008 trackball you'd want a high-torque CIM with some sort of braking mechanism.