You have a problem and you need a configuration language, so you pick YAML. Now you have two problems. Take a leaf out of Rust's book and use something simple and sane like TOML, YAML is a mess. See: https://github.com/cblp/yaml-sucks Otherwise this looks like a great project, please don't ruin it with YAML.
Was hopeful this would leverage TOML as it's built using rust.