Well, I certainly don't know all the features that are now possible since I was away quite some time, but so far I don't know of any way to simulate the ray cluster.
Currently there are two workaround / hacks that I can think of. The ray babies are all build into on subobject that I can let rotate around the mainbody. Shortly before undocking I switch to another model and unleash the babies. Problem: It's not possible to place guns on rotating parts, so the babies wouldn't fire as long as they are docked
Second option I can think of : I use the multidocking feature and dock all babies as single object on the motherbody. That way, they wont "rotate", but I can make them fire (via a trick, the gunmounts are placed on the motherbody, which I will disable once the babies are undocked). Also they can undock with no problem and I don't have to make a "alternative" model.
Currently, I'm favouring the second option. Personally I can forfeit the rotating part.