Just had this idea pop up in my mind. Instead of relying on volunteers mirroring package repositories all around the world, why not utilise BitTorrent protocol to move at the very least some some load unto the users and thus increase download speeds as well as decrease latency?
Most common/relevant/larger distros do that at least for the install/live ISO.
OP is taking about packages and updates using peer to peer, not just the install media. AFAIK no distro does that.