Many users make video of themselves so they would prefer not to have video of themselves changing camera angles. They would also like not having to have a camera operator or ManyCam software operator.
Footswitch control by midi would be ideal since many midi footswitches are available and all that would be required is a “midi learn” function to select the video input. Of course other functions could be programable but this is the obvious most important.
Midi learn is available in all DAW (digital audio workstations) apps, most stage light controllers and apps and other music and audio applications.