Blossom is one approach and probably more reliable, but BitTorrent is definitely more decentralized. Each user could have a copy and contribute, but yeah you run into typical p2p issues here.
nostr:npub1xtscya34g58tk0z605fvr788k263gsu6cy9x0mhnm87echrgufzsevkk5s I belive blossom has that figured out. Each file has a hash and so if you paid to get the file, you know exactly what file it is. I don't see why you'd want someone to seed for 48 hours if you can just pay after you get the file.
Blossom is one approach and probably more reliable, but BitTorrent is definitely more decentralized. Each user could have a copy and contribute, but yeah you run into typical p2p issues here.