Today, the --reuse option of cml-runner does not care if the runner is in use or not.
While it is convenient when multiple jobs can be run on the same runner, some job needs a dedicated runner to work (jobs that take the runner resources).

However, we could benefit from runner reusability for this kind of job by introducing a --reuse-idle option to the runner. This option would reuse a runner only if it is idle (option naming to be challenged).