A master fade is a great idea. For moving lights though you'd need to assign the dimmer channels for master fading so Pan, Tilt, Color, Gobo, etc channels are not impacted. Dimmer channels are often the strobe channel as well so you might need to specify a channel range for fading too.
Great idea but a bit more thought needs to go into it.
With Par 56s it'd be easier than moving or FX lights, maybe you can make a couple of fading cues with smooth transitions to off?