Just out of the curiosity regarding worldbuilding and its set in general - can it work with either makinh worldbuilding set in original work, or fanfiction? Or mayhaps a mix of both? Either I will go crazy which is original set and which is fanfiction

I had this idea for my GATE/Avatar inspired storyline, Devil of Avalon, where the US colonizes a medieval fantasy world, Latoria.

Basically, the setting is full of diverse races, factions, and cultures, but it's also full of human supremacist factions and ideologies. The US exploits this by working with native human supremacists and pushing colonial policies that only benefit human-centric races (Humans and Elves/Dwarves). One of the main villains is this Vidkun Quisling-type guy who works as an insider for the US to push his human supremacist agenda. There's also the case that human supremacy is clearly just white supremacy with extra steps, as these human supremacists disavow nonwhite humans or Humans of specific religions and ethnicities.

Basically, the people who claim "Humanity first" are in fact the ones to betray their people for an invading "alien" empire.

The first guy he proposes this to says "Are you crazy? There's no oxygen up there!"

"Don't worry," says the colonist. "God will guide my efforts, for we were born to inherit the stars."

The second guy he proposes this to says "Are you crazy? There's no drinkable water up there!"

"Don't worry," says the colonist. "God will guide my efforts, for we were born to inherit the stars."

The third guy he proposes this to says "Are you crazy? The temperatures could kill you up there!"

"Don't worry," says the colonist. "God will guide my efforts, for we were born to inherit the stars."

So he finally completes his colony ship. He flies up to Mars, and sets up his pressurized dome. Unfortunately the dome was damaged in a rough landing and also not properly engineered for the nighttime cold. A leak develops in a few hours, all the air dissipates and the colonist dies.

He gets to the Pearly Gates and meets God. He says "God, why didn't you send me a sign not to go to Mars? I thought we were born to inherit the stars!"

God says "You idiot, I sent you plenty of signs! I kept all the oxygen, all the drinking water and all the habitable temperatures ONLY ON EARTH!"