Throw this little snippet in a new script slot:
class Game_Actor
attr_writer :weapon_id, :armor1_id, :armor2_id, :armor3_id, :armor4_id
end
To unequip a weapon or armor, use this script call:
$game_actors[ACTOR_ID].weapon_id = 0
Replace ACTOR_ID with the id of the actor whose weapon you want to remove, and weapon_id with whatever you want to change (weapon_id, armor1_id, armor2_id, armor3_id, or armor4_id). If you want it to be unequipped
and returned to the inventory, then just use a change weapon/armor ==> increase command.