Maybe you could try it and report. I would like to know what happens if some of the playlist files are renamed or deleted from the master library.
I am pleased to report that it works remarkably well. My wife's playlists are preserved.
If I rename a file in the master library (that was in my wife's playlist) and then resync the library excluding playlistx.jmd my wife's playlist correctly sees the renamed file. This probably means that MC is using a unique id # rather than the filename to identify files.
In addition, if I delete a file in the master and resync, it is correctly removed from my wife's playlist.
Overall it could not work better.
fyi, I also decided to exclude curplaylist.jmd from the sync so that my wife's Playing Now is preserved.