Holy crap this would be cool. I personally can not think of a better use of an X1 PCIe slot. Hit the link for a photo...

"The DDR Drive X1 is a PCI Express based plug in card with 8GB of capacity, and bootable. According to sources close to the firm, the drive will have a custom and upgradeable high performance DMA Engine, an external power jack with a switching AC adaptor, and will go into a 512 unit initial production run."