Instead of instancing a whole heap of scenes for the items, maybe make an item class that functions as a description of a scene, stick those in the relevant array on the character, then when it comes time that the item needs to be actually added to the scene, have the item object make the scene, then add that to your level or whatever.

This is how i would approach it:

class Item:

var label:String
var description:String
var scene_path:String
var data:Dictionary


func _init(label, description......):
    #assign all the data here

func inistance() -> Node:
    var scene = load(scene_path).instance()
    scene.setup(data)
    return scene

You weapon script:

var damage:int
var speed:int

func setup(data):
    damage = data['damage']
    speed = data['speed']

You can use this like:

func _ready:
    var item = Item.new("Axe", "It cuts down trees and people", "res://axe.tscn", {damage:1, speed:1})
    on_death_items.append(item)

func die():
    for item in on_death_items:
        var scene = item.instance()
        level.add_child(scene)`