It seems to me that this "hash all the things" setup seems absolutely made for IPFS integration, which AIUI would mean that everyone who chooses to seed those nix stores would incrementally reduce the bandwidth burden upon the "main" nix store. I'm not sure if nix hashes take the $(uname -sm) into consideration, so that could be a hurdle, too

I can very easily imagine that it would need to be opt-in, to keep security peeps from losing their minds, but my suspicion is that a non-zero number of actual nix users would choose to turn it on in support of the community