Things that considered adding these to the story.
1. Louise is the Original Hydro Archon in this story, the god that raised her was the supposed Hydro Archon for the sake of this concept.
2. The Oceanids are now Louise's creations and still are found elsewhere aside in Fontaine.
3. Louise, Venti, and Zhongli had this dynamic sibling bond.
4. At Some point, the Fatui will be involved.
5. Her Gnosis is a Knight.
And lastly, Louise returned to her original world with her godly power and shock the entire four kingdoms or the other cast from Familiar of Zero (Kirche, Tabitha, Montmorency, etc.) and entered the world of Tevyat, getting involved in both the Fatui and the Abyss with the Traveler and Louise (If she wants to show herself on front of them after so long).
Your choice, the guy who adopted this concept.
