Thats only suitable for Event DJs like Weddings maybe for a Disco too.
But think of the Situation that 20 People request a Song and the DJ managed only to Play 2 of them, the crowd gets Angry and dont have the Motivation to ever use this unit again.
I dont even think that many DJs want the Audience to know what Tracks they have.
Or did you ever seen that the big Artist Play a Request? They know what they have to Play and mostly the have a prepared set.