Have you tried to create passive - active clustering?
You can do that with 2 physical nodes or 4 nodes.
If it is 2 physical nodes, you need to 1 active and 1 passive jboss instance on the same node.
So you will have 2 cluster --> Active to Active
Passive to Passive
When you need update, you can update on passive cluster, then change load balancer setting to use that cluster. So passive will be start serving. (being active)
Old version of the code on old active will be not be in use anymore.
If there are 4 nodes, you can apply same thing.
2 cluster both of them are serving for traffic. Change Load balancer setting to use one cluster when you want to update. Update the cluster you took out and change load balancer setting to use that cluster.
I hope it make sense.