If you want something like this because you often format and do a clean install, your best bet is just to do a backup. Perform a clean install - then make an image of it. If you find yourself wanting to start fresh, use the iamge it'll take lesss time and hassle than installing os/drivers/etc all over again.
I would advise against partitioning your raid array. You're not going to see any benefit from it in this case and it would be much easier to go with a single hdd to keep an image on.