I don’t see what you can do at the protocol level to improve availability, you still need people storing the file and acting as peers. Some trackers try to improve that by incentivizing long term seeding.

Like the 13.1 torrent being only a patch to the 13 one and listing it as a dependency? Downloading the 13.1 torrent would transparently download the 13 if it wasn’t already, then download the 13.1 patch and apply it. But I don’t think any of this needs to be at the protocole level, that’s client functionality.