The critical thing here is that regular people can help. The archive is already split into many O(GB)-sized chunks. We need to ensure each chunk has many, many copies.

Torrents are a widely-understood, robust way to mirror large files. But there's no "meta-coordination" built in to the protocol. It's not possible, using just torrents, to have the swarm cooperatively assign who stores which chunks. The optimization function here is maximal chunk availability, subject to individual storage limits and reliability (ie: how often they're online).

It should be easy to just press a button to join a shadow library, allocated 100GB, and be part of the mission.

The best effort I've seen in this space is some guy running a script that crawls the number of seeders for a list of SciHub torrents. Users manually pick the ones with the lowest seeds. All very cumbersome, and prone to staleness.

Of course, this is all a technical problem, separate from infringing copyright or whatever. In the same way as torrents being a technical solution for sharing files, in a general way.