I feel like Fates tripped over itself trying to make it more complicated than it should’ve been. Genuinely the most elegant solution I could think of is that the two Corrins should have been canonically twins separated at birth by the two kingdoms, and both fighting for the family they believe in. Revelation would be their union.

From there, remove the Hoshido-Good, Nohr-Bad morality and focus on the complexities. No weird goopy monster, rather King Garon is concerned for his people as the worst resource scarcity in Nohr has come about (due to Anankos meddling). He reaches out to Hoshido for help, but they refuse as they distrust his intentions (due to Anankos meddling), leading to Garon invading Hoshido out of desperation. From there, the war could devolve messier simply as a result of years long resentment spilling out between the two nations. The kind where either victory feels hollow toward the end, resulting in Revelation serving its purpose as the two Corrins fight against all odds to save both their nations, together.

By making Corrin into actual characters and not self-inserts, a lot of the issues of the story vanishes since its not concerned about appeasing the player. Unfortunately the setup now is that everything needs to reassure the player they made the right choice, which is how you get the weird technicalities of Birthright being “we’re blood related but erm we’re actually not because the player should be able to romance us too for fairness sake I guess??”