> I'm not sure I want to install guix on my main Archlinux box, as I don't want conflicts with the existing libraries and applications

That's the beauty of functional package management: no global state is modified. Whatever Guix does is restricted to its own namespace, e.g. the /gnu directory. Every package that is built or installed ends up there and is completely isolated from the rest of the system.

To actually use the software you use a link to a profile (which is located in the "local state" directory of Guix).

You can install packages into separate profiles with Guix:

    guix package -p /path/to/dev/profile -i postgresql

Or you can just run a shell in a volatile environment as specified in `myapp.scm`

    guix environment -l myapp.scm

To exit this environment, just exit the shell.

In summary: it can already be used just like you want, but it's much less verbose :)