It’s one of those things that we’re not likely ever to do I’m afraid.
I agree that it could be useful although the complexity of developing something like this would be huge. It’s like developing a complete parallel version of QuickFile.
I’m not sure how Spotify do this but I’d say synchronising a flat playlist would be far simpler than synchronising accounting records. Also with the expansion of 4G/LTE I think it will eventually become a non-issue.