New music would be weird. It would be stepping away fromt the whole concept of disco. We have some 'new' sounds already I think, nomad cruise engine one and harvester weapon ones.
All the BGM for Gallia is unique to Disco. But I think the rest of the music is fine, it's not awful. Replacing it all would just be a lot of very unnecessary work. I also believe it was mentioned somewhere that the aim of Disco was to be an expansion of Vanilla, not a completely different game, and replacing every single music file would draw away from that dream.
I quite like the sound effects. Some (maybe most) of the guns sound pretty feeble (although Hell Flurries sound so feeble that it becomes awesome), but apart from that I like the noises on the whole. The music is basically what you'd expect - incidental pieces that change with what you're doing/where you are, sparse/atmospheric. I mostly play with the music off and the sound up high, sometimes with my own music on. Sometimes I'll put the FL music back up, and I don't hear it much so it still has some interest. Especially in places I don't fly to so much.
I guess I wouldn't midn some 'meatier' noises for some weaponry stuff, or just in general injecting some bass to most effects, but it's not really something I'm going to go cry about.
I like the current ones. The music feels really atmospheric, especially when you enter an area like the Badlands, that music sends chills up my spine. Not to mention the awesome music that I don't think can normally be accessed (the one from the storyline at special moments, like when Trent takes out Capital Ships). So I reckon they should stay the same.