The major issue with maps with music is filesize.
With maps with BAttle Music, Town Music, etc, another problem would be timing.
As in, when you leave the town, the music might not stop, so you have to listen to two clashing sound files, one of which being, possibly, a bit inappropriate for your area.
So, a long time ago(Appr. 1 year), I thought of an idea.
Use the triggers to emulate the way a Midi file works.
You upload the different instruments/notes' sounds.
Then you use a death counter to keep track of which beat you are at.
You can have the music trigger check for both, location in map, and what part the song is at.
This means that you only need a few, small sound files, rather then a few, giant sound files, though of course it is a bit trigger-costly, but you can still break it up into chunks of 5 notes per trigger, which would probably work well enough.
This would also allow the music to stop when it should, and play the right, and only the right music at the right time.
I'm not sure how practical this idea is, as I've never had a reasonable and good reason/chance to try it, and I understand that it requires some midi skill, but I can't see any immediate flaws in it, and if you suck at midi making, then it shouldn't be too hard to get help.
Ya, I had this same idea around a year ago to...
I wanted to create a music mixer map for sc, but never got around to it beacuse it would be a pretty worthless map. One problem with this is playing many different sounds at once, if you get a lot of different wavs running at once it causes lag.
Seems like a nice idea. However, as you stated, creating the all of the triggers will be a problem. I like your solution to replace switches though, with counters. I have bad luck with switches and they usually glitch up. Yes, it seems like a good idea indeed. You should make an experimental map with it to try it out.