I use one of these, which is eseentially a hard drive version of what you describe: http://www.reghardware.com/2011/09/05/geek_treat_of_the_week_zalman_zm_v

I use one of these, which is eseentially a hard drive version of what you describe: http://www.reghardware.com/2011/09/05/geek_treat_of_the_week_zalman_zm_ve200_external_hdd_case/ http://www.reghardware.com/2011/09/05/geek_treat_of_the_week... It works fine, though I've found the menu selection UI a bit dodgy, it requires NTFS (a FAT32 firmware is available but that can't do DVD-size ISOs), and there seems to be an unknown limit to the number of ISOs at which point it breaks and needs eSATA to recover (disk mode USB doesn't work either). But it's the only similar thing i know of that's available now, and it gets the job done.