hey fellow mini lovers.
I'm sure others have said this around the forum, but what you're suggesting is highly feasible. I know someone has done a successful "usb" adapter mod (with GPS), so 3G seems perfectly capable. The other thing, is if you have one of the Sierra Wireless USBConnect dongles from AT&T (or others I'm sure,) inside it's just a mini PCIe card.
Anyone have any experience in adding a slot to their motherboard? Seems like a fun mod for the otherwise wasted space for where they felt the urge to print "WWAN".