I am enhancing a JavaEE application and the enhancements include using the ANM web service client. The application is clustered with each cluster member having 50 web container threads. So, even with the minimum cluster size of 2 cluster members that makes 100 threads that could potentially want to use the ANM web service client concurrently. Of course that is unlikely to happen but I hope you can see that heavily multi-threaded applications like those hosted in a clustered web application server environment may need more than 5 concurrent sessions. Also, besides 5 being a small number it is also an odd number which makes it impossible to split evenly across cluster members.
The reason we limit the ws API sessions to 5 is because API shares the same session pool with ANM GUI, more API sessions will affect the performance on ANM. I suggest you to implement a connection pool, which will take care the connections with ANM. We may consider to make the max API sessions configurable in the future release.