MQTT: fully customizeable topic line

[eti-ocb]

I want to connect my station to a ThingsBoard instance over MQTT. However, Thingsboard requires the "v1/devices/me/telemetry" topic line which cannot be configured in the current version of the gateway setup wizzard (or so it seems) as it wants to include the MAC directly in the topic (when I would rather need it in the message).

I am running the 1.14.3 version right now, does anybody see a workaround ?