(When I saw smoke I almost thought that there would be a particle system involved, lagging my PC)
This is more of a hidden than it is a flashlight mod. Because you'd be able to perfectly see all the notes you're aiming for and you don't need to memorize the song. Plus, as it is in hidden, the notes get covered which is nearly the same effect as hidden, however you mention a transparency level. So, perhaps it's basically the same as hidden except easier? Yet the smoke might become distracting making it even... But if it's almost the same thing, then what's the point in it?
EDIT: Another thing to contradict myself: But I've noticed that in flashlight, that the whole entire place dimmers dramatically for sliders. Perhaps for sliders in Smoke, we could make it totally opaque making the slider invisible under the smoke?