Why can’t GC games just use a picture-in-picture function for connectivity?
Although such a feature is technically possible, one little-known fact about the Game Boy Player is that it actually takes about 30% of the GameCube’s power to run the device and process the picture and sound as well as it does. Because of this, a GameCube game would have to be designed from the ground up to implement any sort of picture-in-picture display. As a result, the main game would likely have sub-standard graphics and sound, since it has to work with limited resources. In addition, such a feature would likely take up a large portion of the screen, interfering with your view of the main game. It’s an intriguing possibility, but the benefit is questionable, and it doesn’t appear that this is something Nintendo is experimenting with at this time.