An simpler solution might be to just let you make clothing from metal directly.
Check the inorganic_metal raws. Note the item types, such as:
[ITEMS_HARD]
[ITEMS_METAL]
[ITEMS_BARRED]
[ITEMS_SCALED]
[ITEMS_SOFT]
Items soft are clothing. Add this tag to metals and you can make bronze or steel shirts if you want.
In my case I made mithril, a strong, difficult to product but lightweight metal that can be used to make traditional metal items (shields, swords, etc) as well as clothing items. Mithril is made in a forge, though workshop reactions can let you easily produce any substance from any substance. You could make a mithril metal which is produced only by growing and processing a special plant in a workshop. You could even grow adamantine if you so desired.
Also, keep in mind that no matter how tough the material is, one blow that isn't dodged or parried can easily result in death. A single attack that breaks a hand or foot can knock the door out. A prone, unconscious dwarf is unable to defend themselves. They're easy prey. DF doesn't really let you armor tank things because once you drop in combat you're probably dead. Its not like Rimworld or Stonehearth where attackers will ignore downed pawns. In DF they'll keep attacking especially if the dwarf is downed. Minor injuries often lead to death for this reason. Combat skills such as blocking, dodging, and parrying, are vastly more important than armor.