Take a look at Loot project by Dom Hof (the creator of vine, but now mostly known for Loot...:)

It is exactly how you describe, but so so much more: why limit your Halo / skyrim character to one game world when you could take it into any other format and play with it there? NFT composability is a huge topic and extremely exciting in terms of these optionalities. Again: https://www.lootproject.com/

Also see my comment above with some more examples in response to another question...