So, just a small addition of moderate usefulness is what I propose. Umbrellas and sunglasses are supposed to help against harsh outdoor conditions, namely, sunlight (for cave-adapted dwarves) and rain. These are mostly flavor items, to avoid negative thoughts and belching all over the front entrance, but they can actually be useful for evil syndrome rain and deep dwarf migrants (which will probably have to arrive to your fort through the surface until you breach the caverns).
Historical reference:
wikipedia says that both items were known in the ancient times, though umbrellas were more of a royal/woman thing. Most of designs actually featured some kind of folding mechanism, so it's not a modern invention, surprisingly. Sunglasses were less common, probably due to the lack of cave-adapted ancient civilizations, but Eskimos used primitive sunglasses (against snow blindness) since always and gemstone sunglasses were somewhat used in 1100s AD China.
Google says Chinese umbrellas were made from silk and bamboo, but I suppose our dwarves could theoretically use any cloth and some metal (as in modern ones) or non-bamboo wood or maybe bone? Of course the process should take place at Mechanic's since that place is used for so little now (and also because it makes sense I guess).
Talking about google(s), Eskimo brand slit sunglasses can be made from almost anything, but we don't want to remove such an important game mechanic as omnipresent vomit so easily, now do we? Usual glass sunglasses could be forged in the kiln (the glass will probably have to be smoked one way or another behind the abstraction veil), and maybe gemstone shades can make it too? Although in reality not many kinds of gem can really protect your eyes, so I'm uncertain about it.
About the usage: when a dwarf decides to go outside, he checks if it rains and maybe takes an umbrella from nearby umbrella stockpile if he has a free grasp. Simple as that. Same mechanic can be used for sunglasses, but since cave adaption is less random and more personalized thing, it makes sense for them to be ownable like clothing. Deep migrants can come with their own pair, as mentioned before, so goblin scouts won't find the fortress by the vomit trail.