You give to me an amazing idea!
id3 tag not have a standard attribute for store ratio. And think in 3 users rating the same song ¿Problem? NO
We can store in comment attribute text strings like [user:ratio] making so easy the implementation of ratio for subsonic. So elegant and portable, and I think that the ratio for lot of people is better that your only single ratio.
[Joan:3][Ismael:4][Anybody:5]
I hope it's not late for a programming this single solution in a bit code lines. Yesterday came a beta, that means a new version is coming soon and this feature is so important for so much of us.
At least the first step, not mixing ratios or search by ratio, only rate songs.