@alex I likely had read a bit more, it has plug-in storage so there's possibilities there (they talk of IPFS as a potential back-end).

All that said, Bittorrent magnet URIs seem the way to go. I guess you could go as far as "archiving" single files (each gets a magnet URI). "expiring" stale versions apparently has some support in the magnet spec (unclear). Oh, and you could even make all your links magnet URIs