The LSI3008 controller in the server supports more than 200 drives. If you add a JBOD to one of the nodes, this defeat s the purpose of having this server.
The primary purpose of this server is for fail over. In case one of the two nodes malfunctions, you still can access the storage pool of the front bay drives.
If you add a JBOD via an external SAS controller to one of the two nodes and if that particular node fails, you lose the JBOD connected to that node as well.