I am curious about your jmx client UI, I have tried html adaptor from Sun and JBoss, and a swing based one( I don't remember, someone post on theserverside ), they did save me the effort to build my own console, but with some many things under some many categories to monitor/control, I need a better jmx console tool that's easy customizable.
Quake is right on the point about classloader, what we did here is throw exception if old instance is still refereneced. Sorry can't give you the code as it's not my own, but it's very basic once you read the jdk doc.