Seems like a gap in the market if someone steps in with offline sync (even just one-way) and the ability to securely access files from a next-day delivered USB stick.
Two, clearly in the pre-computer world, attorneys were not reviewing 6 terabytes of actual data for discovery. What makes it so big? Is it that you have scanned PDFs in image format (such that it's a reasonable number of pages printed out), or is it that you have new types of data like electronic records that simply wouldn't have been picked up in the old days?