How do I managing MQTT messages with changing payload JSON structure at MQTT Engine

MQTT Engine Custom Namespaces do not handle changing JSON structures automatically due to the way JSON payloads are parsed.

Consider these two message payloads received sequential on topic "a/b" at MQTT Engine:

{
    "level": "value1"
}

{
    "level": {
        "key": "value2"
    }
}