I'm puzzled, how can you do visual cues on a timed crossfade, for example, actor comes into darkened room and slightly opens a curtain and looks outside then opens up first one curtain then the other and the daylight streams in.Easy with a fader in your hand to follow the actor but extremely tricky with multiple x fades and certain to foul up during a season if actor slips with curtain
etc.So I can see why you would want the ability to control manually.