Not to be too pedantic, but, actually, you're not talking about RMI dynamic classloading. Remoting has its own remote classloading facility.
In any case, you've discovered JBREM-1184 "Fix NPE in ClassByteClassLoader.addClass()", which was fixed in release 2.5.2.SP3, which shipped with AS 6 M3.
By the way, as far as AS 6, the issue is irrelevant, really, since the final version of AS 6 will run with Remoting 3. But 2.5.2.SP3 will fix the problem in the forthcoming EAP 5.1.
-Ron