The current "Notify Me" link only works for items that are tagged as "Unavailable". Customers can signup and then later on they will be notified once stock is available for the product.

We would like the "Notify Me" button to apply as well to backorder/preorders. So, customers are notified whenever an item that is in preorder/backorder stage is available for purchase. Customers do not want to lock in their money and wait for a longer time frame but they are willing to purchase once local stock is available. And we would like them to be notified when it happens on preorder/backorder items. But still allow customers who want to purchase add it into their cart and pay.

Using "Unavailable" together with the "Backorder" option does not allow customers to add the item into cart.