We are interested in Bluemix using this as IaaS for our MQTT Broker, where we have device managment and customer seperation via the bluemix account. If I used the Watson IoT Plattform, I have the special requirements for topics an the related payload (which is always json). Is there a MQTT Message Broker like the Message Broker from AWS IoT in Watson IoT Plattform available?
In Watson IoTP the payload does not have to be JSON - though as you say the topic hierarchy is predefined. An alternative is to deploy IBM IoT MessageSight to Linux VSI/BMIs/Containers running in BlueMix.
More info about MessageSight: http://www-03.ibm.com/software/products/en/iot-messagesight
Hope this helps,