Add to playlist while offline mode is on

Sometimes you're listenig a song offline but you want to add to a playlist and... surprise, you can't. My suggestion is add the posibility to add the song to a playlist and when you connect your device to internet sync the playlist. what do you think about? i belive is a good option cause sometimes i want to listen in another moment the song or share whit a friend while i'm in offline mode and i can't, i need to take a screen shot and i realize i have my photo gallery full of screen shots and no songs shared.