The websocket is used to stream the console output to the user. It's just easier to implement it as a direct connection to the node, instead of forwarding it through the panel.
The two main disadvantages are that you need to setup ssl/https on the nodes (but you should do that anyway, even within a datacenter) and that the api of the node needs to be accessible from the internet. Since users will need to connect to the node anyway in order to connect to the game server, the latter isn't a major drawback either.