I understand that forwarding to an external MQTT broker could be useful for some, but within the context of the ChirpStack Gateway OS - Full image, everything is intended to run locally and thus to forward to the local MQTT broker.

These changes alone would not be enough, as users that would upgrade to these changes will have empty configuration values for these settings and thus their setup would break unless we add a migrations script that adds these config options. If the defaults would change at a later time, it would mean we would need to add a new migration script to update the defaults.

I prefer to keep things simple where we can...