Just to keep readers of this thread updated, Jeff and I received this information from Edson:
"[Drools Fusion] is designed to support one thread per entry-point. So, if a session has the main entry point, plus entry points A, B and C, there could be 4 threads feeding events/facts in the working memory. Just each entry-point must not have more than one thread concurrently executing actions on it."
This is good news. Thanks, Edson. I will come up with a propsed plan of attack tomorrow morning and respond back here for comments.