I was looking at my 2TB drive wondering where to start with that mess, let alone my 1TB with just Live Dead and Phish shows..
Why would you need to worry about the Dead and Phish stuff? It's all legally tradeable unless you were dl'ing ripped Dick's Pick and stuff from Phish Dry Goods!
The way to verify the shows would be: checking that the show folders and files conform to Etree naming standards, the presence of the info text file and MD5 checksum file or searching the Etree database or Archive.org for that show source. To date, the only downloads that I have seen that don't meet those criteria are the Grateful Dead complete SBD download torrents by year. If it was a case of getting stuff that was ripped from someone's collection, you can do individual file comparisons against known sources to determine which source a show probably came from, track times are usually a giveaway since it's rare that different sources get cut at the same place...
The most efficient model for consistent music distribution has been the one used by Etree.org/Archive.org. Each live show source was transferred, encoded and seeded with the MD5's generated at the time of encoding, earliest shows were done in SHN and later it was shifted to FLAC. A new show source was considered the equivalent of a Gold Master Disc and it was entered in a database at Etree.org. All subsequent copies of the SHN's and FLAC's were expected to check against those MD5's and if they failed they were considered bad and discarded so that they wouldn't get seeded in the future. It didn't matter what transport method was used for transferring the files, all that counted was that the files were bit perfect copies of the originals.
For example, here is a show I transferred and seeded in 2000
If you were to obtain a copy of those SHN files today, and you verified the MD5's, you know you have an exact copy of the files as they were encoded A DECADE AGO. Now if I were to transfer the master cd's again and encode it, the MD5's would not match, no matter how paranoid an attempt at DAE was made (this was proven back then for all digital transfers INCLUDING DAT>WAV) If you looked across the different formats available, even after 10 years there are still only 4 unique variants in the wild in spite of the show being copied by more than 5000 people. Those 4 variants are only a single format conversion removed from the initial transfer in 2000.
But this was a system that was conceived to preserve the audit trail and file integrity. The issue of legality was not a problem since the bands have given permission to allow for taping and trading of their shows.