2) A minimal server version (i.e. no playback capability) - as long as the libraries could be synced from a PC client.
Hate to bang on about it, lol! But for a server version, there should be no need to synch. The clients should be accessing the data on the server directly. There should only be one database, which maybe holds several libraries. There should be no libraries held locally on each client which the client accesses, that's not what a client does, it would be behaving as a server!
"Client/server describes the relationship between two computer programs in which one program, the client, makes a service request from another program, the server, which fulfills the request."
The current synching process means that, after the initial loading of the library from the server, the server isn't actually serving anything at all when the client is being operated. The client is doing its own serving.