Alliances may desire to set mood music or ambient soundtracks or propaganda tracks per system. Players may make suggestions in the form of theme compatible MP3/WAV files, which cost CCP time to listen to, and hence these alliances should pay for this service. The soundtracks IP/copyright should be held by respective uploaders.
There is no shortage of reasons as to why this is a bad idea. You’ve already identified some (CCP time = CCP money/game development, and IP issues) which alone compromise the idea, and your “solutions” to those ideas don’t address the problems they pose (or all the numerous other problems). This idea has zero merit to it, there is zero consideration to be given here.