Enable customers to filter out products that are not currently in-stock via the product filter
When a customer wishes to the use the product filter. It throws up a set of results which qualify for the attributes they wish. However if their requirement is also time sensitive (for example they need it arriving within a reasonable 1-3 days) and have 0 interest in placing a back-order for an out of stock product. There is no means by which the product filter can account for this for them. Therefore there should be an additional option in the filter that only returns results of items of qualifying variants that are actually in-stock (and therefore capable of meeting their timely requirements) and linked to the existing stock figure in the system.
For example on our website, if I am a customer looking for a Horse rug, of the Weatherbeeta brand, and it has to be in a 5 ft as per the size of my horse's length. This narrows the results from 128 down to 50 but not in stock - the links explain it!