Use Multiple Time Slots when necessary

Based on the size of the cart and/or attributes of cart items, allow multiple time slots to be used during checkout. For example, my bakery can take 10 orders for lightly decorated cakes each Saturday, but we can only handle 2 super-fancy cakes. We have attributes and pricing that reflect the complexity of the cake (i.e. the fancy ones cost $200, but the regular ones are $50). It would be great if we could set the $200 cake order to “use up” 4 time slots instead of just one.