I've been doing a bit of design work for something along these lines: Take the Stack Attack ramp, but instead of having an upper flat area, drop that level down to the floor, in order to create a "trench" of sorts in the center of the field. Near the center of the trench would be two heavy duty steel pipes linking the two sides of the trench. Scoring would be similar to Aim High, except there would be two goals on each side, slightly lower than AIM High, and the scoring object would be foam cubes, rather than balls. Each block fired into the goals would be different values of points, based on the size of the block. In order to aid auto-scoring, a cheap RFID chip would be placed in each block, with a small directional reader in each goal. Small blocks would be worth less points, large blocks more.

For the endgame, whichever team was fully supported on the pipes, and nothing else, would gain a 50ish point bonus, enough to swing the game heavily in either direction.

EDIT: Here's a render of what I mean: