Vinai Koop (author of Grokking Magento) pointed me towards the magento-hackathon/composer-command-integrator Magento package (in a GitHub thread).
This packages adds a deploy-all
command to the Firegento Magento composer project which (presumably) allows users to explicitly trigger an installation of their packages into their Magento system. (As opposed to the current Composer Installer behavior, which only installs when a package is downloaded or updated)