From glancing at what you want I think you're going about it all wrong. If you have a folder for you and then another for your wife, what if you both like the same song? It relates well to relational databases. You're better off just keeping your music stored according to it (not something other than it--you) and then you can use a database to store the information about things other than it. All you have to do is make a new playlist called My Favorites and you can simply drag songs to it (standard playlist) or you can use a smart playlist and then use ratings or something else. I personally use ratings and store a custom rating for each user in the file, such as [Ben's Rating] = 5. Then I can make a playlist that syncs songs that are 4 or 5 stars and it works great. Plus, I don't have to worry about overwriting another person's rating if I just used a single Rating field. The key is that in my case I'm storing the ratings in each file so in the worst case event, such as my MC database getting corrupted, I still have all of my ratings. The only potential problem would be if I lost all my data but in that case, who cares because I've lost the original songs anyway!
But with the MC database, I probably could also (in a worst case scenario) just open the database (Without auto-import updating) and then I could still see the ratings so I could, say, update my newly ripped library (WORST case scenario!). The database is easy to backup. But it stores the ratings, too, not just the files. BTW: I still use rating so we can easily rate songs with stars and with a single click. I then create an Incorrect Rating playlist that lists where the Rating does not equal that user's personal rating. Then, we can quickly go down the list and update 10+ songs very quickly.
If you use this method, then you can have multiple databases of different MC users and they can all see your ratings (if you setup that custom field) and they can even change your rating--but you have a second copy of your ratings in the [Rating] field. So if another user makes a rating change for you, you will have to confirm it in the incorrect rating playlist.