I can think of one use for blockchains:
Create TAPchain, MPMchain, PiperChain
- For each day archive TAP results and MPM builds to long-term storage.
- Create a sorted list of hashes of that content, publish it.
- Write the location of that document and it's hash to the blockchain of your choosing.
When the next legal issue arises, we'll be ready.
The same pattern could also be used for provable data for any type of content we process. Maintain side-chain and publish to a permissionless, public blockchain.
Alternate idea is to use trillian and create a certificate transparency like system; but that's not quite as usable for something that needs to stick around for many years, vs triggering warnings/audits for bad behavior.