Kha'Zix should get an audio cue for isolation targets
Mecha Kha'Zix has this beeping sound that helps to alert you to isolated targets, and it's the only skin to possess an audio cue.
Classic Kha'Zix could get a void-esque cue - think the way that Vel'Koz's abilities sound.
Gaurdian of the Sands uses the same sounds as Classic. Although, I'm not too sure about Death Blossom.