With the change in texture packs to be able to include sounds, I think that a command that plays any sound from the resource pack would be monumental! (By this i mean completely new files instead of just overwriting already implemented ones)

Something like /playsound "name of the file" so that you can: 1. have a larger sound index and 2. not overwrite necessary sounds.

Also you can have sounds be activated by redstone (via command blocks) and at the time you want without it repeating like it would be if you were to hurt monsters.

If this is implemented things like Mass Effect style dialogue choices could be added into the game. THE POSSIBILITIES ARE ENDLESS. Think about this...

You walk into a house and step on a pressure plate which activates a command block with the command "playsound hello"

Then the command would look for "hello.ogg" in a folder in the resource pack

The sound then plays

With this you could have an infinite amount of sounds and the player could have seamingly real conversations in the world

                       Thank you for your time
                                                                        ~Riceville