Someone has already made an custom Emerald Nightmare faction for Reforged:
https://www.hiveworkshop.com/threads...d-only.324618/
https://www.hiveworkshop.com/threads...forged.324905/
https://www.hiveworkshop.com/threads...forged.324901/
https://www.hiveworkshop.com/threads...forged.324897/
https://www.hiveworkshop.com/threads...forged.324883/
https://www.hiveworkshop.com/threads...forged.322313/
https://www.hiveworkshop.com/threads...forged.324876/
https://www.hiveworkshop.com/threads...furion.322484/