Solid question. I doubt there is sufficient copy protection out there. If the big companies can’t get it done (succesful DRM anybody?), I doubt there is an affordable tool that will do the trick though.
You could always use a tool that will allow you to lock the disc to read-only, preventing it from being corrupted. This however means that cue points and such will not be able to be written to the same drive.
In my personal and very humble opinion, as far as the copy protection goes, it really shouldn’t be your concern. It’s not that they couldn’t get all that music from other “unofficial” sources anyway, having it all on one disc just makes it easier. Also the actual selection can’t be protected as it’s very simple to run a track list from a number of tracks in DJ software or outside of it.
MP3 info goes with the tracks. This means you would have to have the MP3 data up to date before write-protecting the drive. Making it your responsibility.
In most software (can’t remember for Serato but I believe so too), it’s possible to have the tracks and the analysis files separate. This means if you give a DJ a write-protected drive, he can just hook it up to his laptop, run Serato and have serato do all the beatgridding and other analysis and write that to his LOCAL harddisk. This is also where cue points and such will then be kept (that stuff is all proprietary and doesn’t get saved with the actual track).
So your DJs would have full creative control over playlists, beatgrids, loops, cues and all such, but not on track related info that is stored in MP3 (like artist name, track title, comments, etc.) Combined with a write-protected disk, that would get close to what you are asking for.
From an IT point of few, I’d invest in SSDs rather than HDs in your external enclosures. Reason why is that there are no moving parts. This greatly reduces the risk of HD crashes and malfunctions.