Just a quick comment, not to derail or deflate your need/inquiry. I certainly don't want to offend anyone by my comments.
From a logical standpoint, that machine will go through hours and hours of just patching alone. For me, i'd rather go back and update my image every so often (once a year, twice a year), rather than installing from scratch. From scratch, you are talking pre- SP1, that alone using WU, takes up to a couple of hours, when it finishes applying the SP, and reboots 2 or 3 times. This likely can be shaved down some, by having the SP1 already "downloaded" and deployed in your template somewhow, but....Can you imagine applying an image template to an older 5 or 7 year old machine? While I may not help with your technical question if it is possible (which I assume it is) or how to do it, for me the patching alone would detract me from even attempting.