When creating a new a new LoadBalancedRSocketMono you pass in a Publisher<? extends Collection> that emits a collection of RSocketSupplier factors. The collection that is emitted is the current collection of RSocketSuppliers that you want to load balance against. In your case an RSocketSupplier could map to a server node. As new servers are scaled up or down the factories stream is should emit the current collection of available servers. This could be a stream like this:
on next: <server1>
on next: <server1, server2>
on next: <server1, server2, server3>
on next: <server2, server3>
What you need to do is create a Publisher that emits a collection of RSocketSuppliers that represents the current collection of servers nodes. As servers come and go the Publisher needs to emit a new list that is the current snapshot of servers.
What are you using for discovering new nodes? I might be able to help with a Publisher<? extends Collection> example or point you in the right direction.