Logging changes/events to remote MQTT server as JSON payloads

Probably not, at least not easily. In OH 3 it’s totally possible but PaperUI doesn’t support all the needed rule triggers.

What you are looking for is Marketplace MQTT Event Bus

Or you can set up and configure an Generic MQTT Channel for each Item individually and link them to all your Items using the follow profile. But that would be a whole lot more work.