The idea for this request should be pretty obvious from the title. It's been a while since I did a request that isn't Bleach related, so hopefully this is a nice break from that. Anyway, in this request I want Aether and Lumine to not only keep their powers after encountering the unknown god, but I want them to also not get separated.
I then want the twins to meet Paimon the same way it happens in canon, and then I want them to encounter Venti and Dvalin differently than canon. Instead of them startling Dvalin and him flying away, I want Aether and Lumine to purify and save Dvalin right then and there, with Venti as an eyewitness. Venti takes them to Mondstadt, where they explain what has occurred and that the Stormterror threat is over. After some chapters focusing more on Mondstadt and the interactions between the twins and the characters living in the city, (and a particularly interesting encounter with Albedo), Signora arrives to try and steal Venti's gnosis, but fails due to the twins' intervention.
Following that, they decide to venture to Liyue, and here everything goes about the same way canon does, excluding the fights with Childe and Osial, where Aether and Lumine win very quickly. Since the people of Liyue aren't really the ones that win the battle, Zhongli doesn't give up his gnosis to Signora. After that, include some interactions between the twins and Liyue's citizens.
Have the whole thing with Dainslef go differently than canon, with Dainslef being suspicious of the twins and not trusting them. No scene happens after the final fight with the abyss herald, and no one appears before them in general, since there is no twin that is being searched for.
Aether and Lumine then head to Inazuma; Lumine decides to take the canon route via ship, but Aether decides to just fly there despite the weather, and given his experience in other worlds, he makes it there perfectly fine. He lands discreetly some ways off from the shore on a random island, so that he doesn't draw attention to himself. I haven't finished Inazuma's storyline just yet, but I'd assume this is where the most canon divergence would occur, with the twins opposing the raiden shogun and all. Once that story is concluded, have some interactions between Aether, Lumine, and the people of Inazuma. Since I've only gotten to the part of the Inazuma storyline that is the Signora fight, that's all I can really say for the nation/region of Teyvat that is Inazuma.
From there, either wait until Sumeru's release and continue after that, or make up your own story for Sumeru.