This should be in 1.7 but at least we can plan for it. I honestly don't like this solution entirely, because you'll have to map every XML file that has virtuals you rely on. But at least with some careful coding, all addons should be dynamically loadable in 1.8.
* You'll be able to include references to FrameXML files in your .toc file (e.g. ..\..\FrameXMLFonts.xml) to get default virtual frames during on-demand loading