Unequip all gear > choose gear you want to change to severing > Deactivate gear copy
once done, you can still equip the other unequipped gear you have in the inventory on your copied character
havent tried copying the gears again once unequipped, you might have to use the refince caphras catalysts again so im not sure take this with a grain of salt :D
ps. you cant change the copied gears to severing / cant copy severing gears