Stage 2 seems problematic at least the way I see it. Most users have at least a thousand derivations- is it possible to fuse mount each one?
Also: I think some people are unaware that Nix hashes are not content addressable. The best solution (which OP is proposing) is probably to use the .nar hashes in IPFS which is content addressable.
Also: I think some people are unaware that Nix hashes are not content addressable. The best solution (which OP is proposing) is probably to use the .nar hashes in IPFS which is content addressable.