Alpha only works (in the compositing sense) if there is nothing behind it. You are wanting a “put a hole through everything here” kind of thing. Don’t know if it exists. But…
-Render the ground/card as a seperate passes or,
-instead of alpha use a matte color in the same spot, composite using chroma or,
-place alpha on the ground behind the alpha on the card or,
-bring the footage into C4D and composite there…
probably more ways…