Let me start out with a simple question - how are you planning to handle the Window 7 licensing? To create a single image which you then "duplicate" to other machines requires a Multiple Activation Key (MAK) license as a standard retail license is not intended to be used for multiple machines, and it is likely that activation will quickly stop working if you try this with a retail key.
The mechanics of cloning a gold image to other machines is quite straightforward using Ghost Solution Suite, Paragon Partition Manager, Acronis, or any of the other imaging solutions available to you. I would suggest using a USB hard disk rather than a key as the performance of keys is quite slow unless you buy a top of the line key (probably more expensive than a hard disk). Also, if you have a large image, you may need to reformat USB keys to an NTFS file system.