Supposedly the GameCube video interface can output a 3d video signal when DLR is set. In testing, when enabled, gcvideo glitches out and displays a corrupted image.
I think it would open up homebrew to a new side of the GameCube, adds more functionality to gcvideo and leaves room for the diy 3d community projects out there.
Hardware registers - https://hitmen.c02.at/files/yagcd/yagcd/chap5.html
(Yet Another GameCube Documentation)