Custom 'Preorder' and/or 'Special Order' availability filter

Out of stock products that are included in preorder offers show up as ‘In Stock’ in collection and search results pages. This is unclear for customers. I would love to be able to assign preorder offer products to a custom filter that is not ‘In Stock’ or ‘Out of stock’ but ‘Preorder’ or, if possible, a customizable name on a per offer basis, as some items I sell are pre-orders for incoming inventory with a definite ship date while others are special or custom order with an unknown ship date.