I wrote a small driver called dbus-mqtt-services (https://github.com/sebdehne/dbus-mqtt-services) which listens on a special MQTT topic and creates new services on the dbus as instructed in the MQTT-message.
This allows you to create whatever service you desire on the dbus without having to install/run any code/driver on the VenusOS device. Just publish the desired service data onto this special MQTT topic and the service is being created (multiple services are supported). Subsequent MQTT message just updates all values.
I used this driver to bring my own battery-service on the dbus - which supports multiple Daly BMSes and reports all the data as as single battery to the Victron system. Se victron_daly_bms_service (https://github.com/sebdehne/victron_daly_bms_service)
So, instead of doing this:
This driver allows something like this (or any other type of service):
The code is a bit raw and not very polished yet (I just made it all work), but feedback is very welcome.