I was just telling one of the other sound guys here about the stereo in an old my car my parents used to have… it’d immediately turn on and start passing signal, even before the amp’s caps were filled up. As a result the volume would fade up over maybe a 1/4 second or so, and you never gave yourself a heart attack because you forgot the radio was cranked. Just that little bit of volume ramp time was enough to make it not startling, no matter how loud it got before you could grab the knob and turn it back down.
Anyway, I was just thinking it might be nice to have the mutes and/or mute groups optionally fade their channels off and on to avoid startling you (or the crowd) half to death when you accidentally unmute a channel that already has signal.