Does this could help?
http://agnipulse.com/2009/07/boot-your-usb-drive-in-virtualbox/
It's a procedure to boot USB sticks into an (empty) VM of VirtualBox, I did not test it yet because I'm at work, but seems doable.
Note:
1.this is for Windows based VirtualBox only
2. not (yet) an idea on if/how this could be automated..
ciao a tutti
carlo