I would like an option in the config file, where you can specify packages to install and start before Mosquitto.
My motivation behind this is I want to connect HARDWARIO Tower to my HA, which communicates through a Radio Dongle (it sends JSONs on the Serial port) and has a util called bcg that runs in the background and turns the serial data into MQTT messages.
Possibly, yeah, but imo it would be easier to start the utility in the same container as mosquitto, as bcg is already done and works on any other system, Linux included.