I want to create an MXML container component that has some of its own chrome -- a standard query display, et al -- and that supports the addition of child components to it. Something a lot like the existing mx:Panel class, which includes a title label, but acts like a plain mx:Box with regards to adding children.

What's the easiest way to do this?

Edit:

To be clear, I want to be able to extend the container using MXML, so the "Multiple visual children" problem is relevant.