maybe replace Passenger with uWSGI?
Toushirou would benefit from having less load and uWSGI is told to be quite efficient. The Emperor component would be able to manage a dynamic drop-in for all configurations (YAML supported).
Mailman is planned to be upgraded and the package seem to enforce using uWSGI. So I wondered what was the state of the project and it seems interesting. Ruby, Python and also Perl is supported, and it is clearly more tweakable than Passenger. For example the tyrant mode could be used to provide more security. Workers also are monitored, restarted and fork bomb protection is provided… so this seems appealing.