I've thought a little about, for example, building something that could slice just the needed utility functions out of a Shell utility library. (Not really for minimizing the dependency graph--just for reducing the source-time overhead of parsing a large utility library that you only want a few functions from.)
Would obviously need a lot of toolchain work to really operationalize broadly.
I can at least imagine the first few steps of how I might be able to build a Nix expression that, say, depends on the source of some other library and runs a few tools to find and extract a specific function and the other (manually-identified) bits of source necessary to build a ~library with just the one function, and then let the primary project depend on that. It smells like a fair bit of work, but not so much that I wouldn't try doing it if the complexity/stability of the dependency graph was causing me trouble?