What I want as a developer is to establish my trust relationship to developers of libraries I depend on.
`npm install <somepackage>` should first check a record of signing keys in my source code repo, then check a user-level record of signing keys I've trusted before, and then - and only then - add a tentative trust relationship if this is brand new.
`npm release` or whatever (npm is just an example - every system could benefit from this) - would then actually give me the list of new trust relationships needed, so I can go and do some validation that these are the packages I think they are.