How do changes (like star ratings) affect multiple users?

[espd]

I see. The limitation of using regular iTunes sharing is that we can't control ratings and such.

What we want is to:
A) Share the same library of files, located on a separate host — the Mac mini.
B) Consolidate our libraries of music files without having to lose the ability to individually rate and sort and generally interact with iTunes the way we normally would.
C) Stream those files from the host mini via Airport.
D) Be able to separately create and control playlists, make separate ratings, play different playlists at the same time, without affecting the other person's ratings, etc.

I suppose we could consolidate the files on the mini, then run separate instances of iTunes that point to the "Music > iTunes" folder on the mini instead of on our local machines. But then I suspect we'll both be accessing the same "iTunes Library" and "iTunes Music Library.xml" files at the same time, which might cause problems and almost certainly conflicts.

Perhaps someone knows a way to point her copy and my copy of iTunes at different "iTunes Library" and "iTunes Music Library.xml" files, while pointing at THE SAME "Music > iTunes" folder?