Rather than having dragonhide items be generically “dragonhide”, let them each be a certain dragon color, which cannot be specified by wishing. This item does not confer the same extrinsic it would if it were body armor. Instead, when you are wearing dragon scales or mail and a dragonhide item of the same color in another slot, you gain a very powerful extrinsic which cannot be gained otherwise. E.g. cancellation immunity for gray dragon armor.

The idea is to discourage everyone continuing to wear gray or silver dragon scale mail: if you find or wish for dragonhide gear and get some other color, it may be attractive to wear dragon scale mail of that color instead in order to get the powerful extrinsic.