Additional option for the "add to cart behaviour when out of stock"

Would like to see an additional option under the "Add to cart behaviour when out of stock" setting. 

Currently, the options are either "allow adding to cart" or "do not allow adding to cart". 

I would like to see an additional option of "allow adding to cart - with notification". There should then be a text box where you can enter the message you would like displayed when a customer tries to order an item out of stock. Something like: 

"Please note this item is currently out of stock with our suppliers. Should you proceed with this order, this item will be placed on back order. Please contact us for estimated re-stock dates".