I reject your idea that it could allow copyright laundering. A copy of Mario from my video is still a copy of Mario. My license to play the game allows me to incorporate my gameplay into a new work, but extracting that character from my work arrives at a character indistinguishable from Nintendo’s.
I would not be violating Nintendo’s copyright to license my video to Montendi, but Montendi would be violating Nintendo’s copyright when they extract that character and use him in their own game.