WSO2 IoT server itself can be used for your purpose without a problem. You don't need to integrate lorawan-server and use WSO2 server as a MQTT broker here.
I was able to successfully try out their Raspberry pi sample. There they explain how to use their MQTT broker to establish the connection between the Raspberry pi and the WSO2 IoT server. They do have data analytics capabilities and support major databases like H2, MySQL, Oracle etc. Refer here
(https://docs.wso2.com/display/IoTS310/WSO2+IoT+Server+Analytics) for more details.
What this sample simply does is;
WSO2 IoT Server provides a sample Raspberry pi agent (we can customize it as we want). This Pi agent publish temperature sensor data to the MQTT broker and server picks up those data and use for analytics. Also from server side we can send commands to the Raspberry Pi too. In the sample they provide, they allow us to on/off an LED bulb which does the same thing where server publish certain data to a MQTT topic and Raspberry Pi agent listen to that topic and picks up the command and executes it.
You can see more information about this here (https://docs.wso2.com/display/IoTS310/Raspberry+Pi).
Likewise they have allow anyone to write any custom device types using the set of API they have provided. Refer here (https://docs.wso2.com/display/IoTS310/Creating+a+New+Device+Type). Also they have provided a Maven Archetype in order to create our own device type plugin. Refer here
(https://docs.wso2.com/display/IoTS310/Creating+a+New+Device+Type+via+the+Maven+Archetype).
