Before my sons left the nest all of their music was combined with mine ... as they grew older, they started to like more and more my Rock, Jazz, and Classical stuff, and they gave me a taste of what good hip-hop and electronic music is in return. SO in a way I'm sort of in a similar situation as you, although I'm really the keeper of a master "family" library.
So, if you can all agree on a standard ripping "mask" or template so you don't need to mess too much with repointing anything other than a drive letter ... there are a bunch of things you can do .... but easy .... not really
1) Basic syncing, you can all define which fields would be truly user fields and fields which you only modify if there are errors ie. The Album Artist, Artist, Album track name become sacrosanct. In your example if they want to separate versions by album name rather than use use a "version" field you are going to have problems. This can be a mess if people do not agree on genres etc. But if there are only a couple of fields like ratings, you can just mark the fields you want to be individualized to not write the tag to the file and be library based only. Pretty hard to get everybody to agree on things though so probably not the best scenario. And frankly its a real PITA in practice.
2) One person's library is the master and this writes tags to the file; things like ratings would not be written to the file again, but before syncing the physical files, you would create playlists for all five star, 4 stars etc. All you need to do is pull up the playlist select all files in the 5 star list and retag once. Done. Review all tags that write to the files and remove only the most critical ones, that way you can use syncing software instead of copying 4tb worth of stuff all the time, when there have been no changes. However, if you have a significantly different tagging system this is still not great. You can also play with the option to not update the library for external changes, depending.
3) Have an archive copy of your media files -- clear all tags on this cloned drive (or keep only the "key" tags in the file. Probably have to do this in an external tagger, not sure actually if you can selectively clear only specific tags in JRiver or not). If the filename/path contains: Album Artist, Artist, Track number, track name and maybe some rule to differentiate versions and disk number. The basic metadata can be simply rebuilt, but you will have to tag new music yourself as per genres etc. When finished syncing, you can select the files and use the library tool and update tags from library. This is pretty easy to do, but lots of problems can crop up.
4) This is what I do now.
You only share new music that each family member has ripped/downloaded. If the ripper permits, auto tag a field (I use keywords, but you use what you want) so that you know who bought the music. Set-up views or a smartlist based on the keyword and date imported (or another date field if you prefer). So eg. there is me and my 2 sons .. so the tag might Say Papa, Son1 or Son2. Make two of these views for each ... so I know that all music to give to son1 comes from Papa and "Son2". Son2's view will have just the music from Papa and Son2. Each of my sons have the two views. Now either son can share their stuff together or with me or as it works out each one of my children get my music and their "other" brother's and they are only transferring the music they purchase.
This is date filtered so for instance if you have added 10 albums one comes over and I give them a copy. Right away I change the date in the view for that night. So you are only "syncing new music. Then you "sandbox" ... meaning that you set up your import to include a temp directory for this new stuff; then each person can filter the new music and verify and retag if necessary. When satisfied you can use the Move, rename, copy tool to move it into the main library path. (I have a second field to tag if they have been verified or not. In this way, you can write what you like to the files and as long as each person tags their rips/DLs and each person changes the date on the views after a transfer, I find the best of both worlds. The only down-side, is you might have to do a lot of retagging, but I'm pretty obsessive about my tags, and my kids could care less or are more interested in DJ tags.
There are other ways I have experimented with ... like separate libraries and such, but once you get the "family" collection set-up initially, I find it painless. If you mess up and forget to reset the date field or for some reason people don't fill in the who ripped what field ... just setup a good duplicate smartlist and erase the dupes from the sandboxed (temp) directory. Another benefit is that these "transfer views" all you need to do is select all and use the MRC tool again and copy them to a usb key or drive. No need to mess with selecting stuff manually via Windows. Once the first "batch is copied", you are not adding hundreds of cd each time so it becomes really very easy, and not difficult to setup (well you need to know how views work)
If you really want to toy with the first couple of options, just make doubly sure you have multiple backups of the JRiver Library files. I'm sure there are other ways to do this. Sharing physical media like this is doable (euh make sure its legal right
- don't forget to support your artists!! ). Sharing metadata is a lot more complicated. You can share a backup library file, but you need to know what you are getting into, and what you are describing is not one master library. I think it is better to have independant "main" libraries for each family member.
Of course you have to maybe train your "family" members so they are not JRiver noobs, but I set up my sons systems for them and they just have to have a little discipline and not be total couch potatoes.
Hope this helps