In Section 4 The Game, there's a new definition of SHOOTING MECHANISM. There is no definition of MECHANISM in this section, therefore the definition found in Section 5 The Robot applies. The definition for SHOOTING MECHANISM is a subset of MECHANISM in general.
Clearly this applies to rollers, belts, etc used to pick up the balls that could be reversed to release the balls - they impart a dynamic impulse to the ball, so they are a shooter.
However, this would not apply to a trap door MECHANISM. That does not impart any force to the ball - gravity does that. Gravity doesn't qualify as a MECHANISM under Section 5 because it is not a COTS or assembly of COMPONENTS. So any aiming extension (fold down door, etc) that directs the balls toward the corner goal should be allowed, provided that the balls are only rolling downward.
This is supported in Q&A
http://forums.usfirst.org/showthread.php?t=429 (previously quoted in this thread) because of the warning about becoming a wedge. In answering this question, the GDC implied that the ramp might be outside the original footprint, thus the warning about <R04>. If the ramp MECHANISM had to stay entirely within the original footprint, there would be no wedging possible, unless the ramp was designed as a leading edge with no bumper.
Even a dumper hopper, as shown at kickoff, does not fall into this category. While the MECHANISM moves, it is gravity that imparts the
final impulse, not the hopper. The raising of the hopper is no different than any other MECHANISM that lifts balls from the floor - it imparts potential energy to the balls in raising them, but does not deliver a final dynamic impulse.
Just my opinion, I could be wrong.