[CMCDragonkai]

Nix helps with this. There is an optimisation pass that can create hardlinks between similar packages/files? There was recent talk on package deduplication. Also every package directly specifies every dependency. However it currently won't help to remove unused files in each package, that violates the immutable hashes. The solution is to create more granular packages or to leave the immutability zone and into the mutable world if you have embedded scenarios.