The fact is that every player has their own take on what they should be hearing. With that in mind, I would like to nod towards EVE Onlines current soundtrack. It is no longer a collection of tracks, but a variable file, dependant on the location and situation your ship is in. If your in the safer regions of High-Sec Empire space, mining a few asteroids then the music is quite light hearted and calm. When you get into fights in more dangerous space, the music becomes harder, edgier and more sinister.
If this could be achieved through variable samples keyed to locations and situations, it would be awesome.
Another big thing for me would be the capacity to choose an overall theme for the music. I would love to be able to choose between styles, like Dark Wave, Industrial, EBM, Nu Metal and others besides. I think this would be a huge step in the right direction for giving a truely unique gameplay experience.
Lastly, a jukebox option, where the player can upload their own locally saved playlist. This would be awesome.
Am I asking for too much?