There should be a villager that trades music discs for emeralds. This would replace the highly arbitrary function of having a skeleton shoot a creeper, and would make it much easier to get music discs.
I dunno, getting a skeleton to shoot a creeper is one of the first little challenges added to the game. It's always been like this and it's just so... ingrained in many people's minds.
I think the way you acquire music disks should stay the same, but villagers actually making fair trades and trades that you would actually want to do would be great.