No way to make the handler an MBean at the moment. Would not count on the JMX invocation handler for a while (as will be when I get to JSR 160, which is a ways out).
It wouldn't be that difficult to call on the handlers via JMX and just specify the object name. What's the use case for this (not that I think it is a bad idea, just curious). If this is something you really want to see added, please create an issue for this in jira.jboss.com.
No current requirements, I just thought it would be cool :-) Actually, I'm thinking make it an MBean to allow for inproc calls more efficient (if I have an client inproc with the MBeanServer, would be better to make a local JMX API call as opposed to going through the remote layer and incur the penalty of (un)marshalling)?
Is a good idea to have it, so will create a jira issue. BTW, remoting will do in process calls automatically if sees that the server and client remoting invoker live in the same jvm.