[MetalJacket]

As long as your robot is not physically in contact with the discs you should be fine so long as you are only pushing 4 or less disks at a time under the goal. There are 3 problems I can see with this is that 1. the oposing alliance could just chose not to introduce any game pieces until one of their robots is ready for them thus preventing you from hoarding them (since hoarding yours would be pointless), 2. Why not just take them and score them yourself if you have them, the only alliance-specific game pieces are the colored ones for the pyramid goals, and 3. If you're not careful and build up a pile of more than four touching one another, it may be ruled that you are controlling mor than four if you push more under there.
-just my opinion of the rules/strategy