[mrnoble]

If "assists" are a major component, and "hockey" is the inspiration, the GDC doesn't need to go through anything so complicated as dividing the field into three zones, with robots restricted to each zone and therefore encourage passing. They could just do something like:

Scoring increases with each "assist" pass. Low goal (or single robot touching the ball/puck/whatever)=1 point. Middle goal (or two robots touch the game piece)=3 points. High goal (or all three robots touch)=9 points.

Or something like that.