If we go that route we'd need to update the CI script accordingly (to expand the template on top of looking for upgrades)

Did you also want to add this testing dockerfile to the CI ROS 2 images workflow?
https://github.com/osrf/docker_images/blob/master/.github/workflows/ros2_ci.yaml

Did you also want to add this testing dockerfile to the CI ROS 2 images workflow?

Nevermind, looks like we're not yet calling .ci/ci_script.py from the CI ROS 2 images workflow anyhow.