Allow item count in result field for crafting_transmute

With the latest snapshot, it's possible to transmute items with a crafting recipe in a datapack. This way you can modify existing items and add to them. 

I'd like to be able to create a recipe that duplicates the item when i craft it with - for example - a diamond. Like this:

{
  "type": "minecraft:crafting_transmute",
  "category": "blocks",
  "input": "minecraft:player_head",
  "material": "minecraft:diamond",
  "result": {
    "id": "minecraft:player_head",
    "count": 2
  }
}

Unfortunately though, the result field only accepts a string, so I can only use "minecraft:diamond", and not specify a result count.