1. Set up a file server with lots of security.
2. Person #1 uploads stereo MP3 reference track of new idea.
3. Person #2 downloads stereo MP3, makes a new session for himself, creates something, uploads individual stems of a contribution to that idea. Say, arbitrarily, piano left, piano right, acoustic guitar 1, acoustic guitar 2.
4. Person #1 adds #2's tracks to his mix, then posts another MP3 ref.
5. Person #3 re-creates step 3.
6. Person #1 repeats step 3.
Eventually we have a "meeting" about that piece of music and pare it down to its essentials. Then someone mixes it. This is at least the way it works with Digital Noise Academy.
Best,
JMJ