I was recently writing guix.scm files for my projects and was having problem with the libraries I added, not being found inside the shell. After struggling for hours I finally learned that that the LD_LIBRARY_PATH is not being updated automatically inside the guix shell environment so the libraries can be found easily.
So my feature suggestion is that maybe we can have a flag or a option for guix shell, something like --add-ld-path or --update-ld-path for example, to add all libraries specified in the guix.scm or even as sub-command guix shell --add-ld-path mesa as an example, to automatically update the LD_LIBRARY_PATH environment variable to contain the correct paths to these libraries so they can be found easily inside the shell.