(Endwalker spoilers)

I think it makes perfect sense for the Garleans to switch back to a republic. They tried having an emperor. Less than a hundred years after putting him on the throne, their country is totally leaderless because everyone who could take charge is dead, brainwashed, or gone with no plan to return; the remaining population is hiding from deathbots in a subway station; and a despair-monster that used to be the emperor's uncle is brainwashing people left and right. The republic clearly had its problems, but hereditary monarchy has not made itself look very good.

I do like the idea of switching out some of the Scions for people who aren't from Sharlayan/academics/white-haired, though. A Garlean machinist might be nice, since the Scions don't really have anyone with tech skills who isn't occupied with Ironworks business, or a consistent ranged physical DPS. If you want character development for Alphinaud, I think that might be an interesting way to do it. He can keep protecting people as a healer, not a swordsman, which I feel is an important part of his character, but they could maybe get into the same character type as EW!Fordola - someone who's done some horrible things and has serious emotional issues, but is really working on being a better person.