Ghosts in df can definitely interact with objects. One variety will randomly "misplace" objects (actually they can go through walls while holding the object right? Im pretty sure i saw that happen while i was watching one) and others will batter dwarves to death. So presumably ghostly kobolds can touch all the shinies they want or something.
And yeah, theyre always naked right now. Nobody wants to see naked kobolds but too bad. (or dwarves, i guess) Toady might give them ghosty clothes in the future but undead dont spawn with possessions of any sort right now, except tower zombies. Something about coding problems with treating corpses as containers iirc
whats more mess up is the game does have a item storage container for dead people if you resurrect them via dfhack, as dying again after that just poofs the character as they already had left a corpse.
also undead in towers are peasants in towns but with the undead syndrome class type slap on, going by the site inhabitant's coding goes. so the game clothes them already, other wise the undead the necromancers make are naked punchy types.
this doesn't mean player necromancers with a lil modding can't force items and weapons on their undead via granting them can speak and can learn, it's just the process will take ages to build an armed zombie force, and they probably don't get skills to fight well enough.
that said ghostly clothes seems like something you end up with a player(me) trying to harvest the clothes off of the dead and gaining insane enchanted items that probably means DF modding the raw materials into building blocks or weapons.
also dfhack ghostly flag would end up either turning adventurer's items into ghostly items, or figuring if the game clones a dead unit's items which leads to seeing if ghostly items has a value in stores, also giving folks valuable items causing them to die in a fort, then stealing the ghostly version of the item they had.
oh and in a weird adventure mode check ghost adventurers can't seem to move through solid objects if they are wearing or holding any items so a kobold could pick up a shiney, but said shiney can't be noclipped into the ground making the player of the fort super confused on how this item is embedded in slate 3 z floors down. combine that with the no nonflying being as a ghost can fly the kobold can just swim through solid mass but has to walk like every one else, or risk stuck floating in one spot forever.
besides it not the ghost kobolds one has to worry about but the mummy kobolds