Let's say you have multiple attributes with more than one that can apply to multiple products, maybe food.
So maybe I have organic, egg-free, gluten-free, dairy-free, nut-free, etc. Since each product could have an array of these options, using a multi-select attribute seems to make sense. However, since there are thousands of items, this is not practical being that we cannot use the "update attributes" in the actions to mass apply multiple attribute options since not every product has all of the same options in the array.
We also want the filtered results of these attributes to be selective, not additive, so we narrow the results to only the attributes selected in layered navigation. This does not work with multi-select attributes as a default. All products will appear for each selected option.
We would like this to appear as a single "Specialty" attribute or similar in name with the list of available options under it in layered navigation allowing the user to choose multiple options such as dairy-free and organic.
Please make suggestions how this might best be accomplished.