If Lux ever gets a "rework" with other mages like marksman did, she should get a blind.
Because why the hell not ? Champions tend to have more and more passives, and i really think that if Lux procs her actual light passive on a target two times in a row (Q auto E auto) the target should be blinded by all that light for a brief duration. Would separate THE GOOD LUX and the BAD LUX.
If not, you could always make her laugh global if she is on a killing spree and louder the more kills she gets.