fyi - here's an example MQTTSubscribeService section with annotations in case anybody has interest. See the attachment for which sensors are handled. Should be obvious.
Items marked FIXME aren't directly mapped to weewx db elements in this example, but some light editing would be needed regardless to match your setup of course.....
Lastly - MQTT is now supported on the GW1200 gateway and WS3802 console if you update the firmware, so it seems like Ecowitt is adding support to older models of their gear as time passes...