No sense in duplicating the site, with some minor backend modifications that would allow you to have an additional order status type, for example, I add a online purchasable item to my cart, as well as a phone only order item, the custom order status would be assigned to let you know its a mixed order. You could even add another order status field JUST for phone ordering products only. I've setup similar sites before who "pre-sell" items as well as in-stock items, its just another means of keeping a "status" on the orders your customers are placing.
hth.
