Oh boy, here we go with the same old tired argument that Garlemald needs to stay an empire due to "variety".
Most states in the game are not democratic to begin with, and those that changed their governments each had a completely valid reason of doing so. Each had lost their entire ruling class and had recent histories of absolute monarchs becoming tyrants that ruined their countries.
Garlemald was a democratic republic for 600 years. The empire was specifically built by an outsider who had no love for the Garleans or Garlemald and it was intended to fall apart. They had two civil wars over the succession of the throne that destroyed the homeland and killed scores of Garleans. The Garleans ended up destroying their own empire by themselves without the need of rebels or revolution and that happened before Endwalker so the expansion can't be blamed for that. What point is there to keep an empire going when the capital city is a pile of rubble and every single time a leader dies, the legions fight each other and kill their own people?
Aveyond's fanfiction is poorly researched when it comes to the lore we know on Garlemald, which is to be expected of one who has Russian in the Cyrillic script in his signature representing Garlemald despite the fact that all the people, places, and objects named by Garleans are in Latin. His story has a pretty, blonde Grand Duchess (title that doesn't exist) become heir to the throne (women aren't allowed to, according to Garlean society), with a super special unique Russian/Hrothgar name instead of a Latin one (Svetlana) get locked away by Varis because she liked a non-Garlean before coming back and taking over the empire. The senate is portrayed by Aveyond as being evil and doing acts of terrorism against the general populace and assassinating nobles despite the fact that in the actual game they're a powerless and divided faction with different ideas and one of the factions themselves is purged by Varis. That little tidbit coming right after a preachy spiel about how "democracy is bad and the empire knows better for its people" and Alphinuad being laughed at for "pitching democracy" feels like bad writing and a giant over-correction based on the writer's views.
But sure, the denizens of Garlemald would be thrilled to have another Galvus on the throne because the past year has been AWESOME and the Garlean people will put their full-support behind their new empress, a Garlean woman pregnant with a baby from the leader of a recently rebelling province despite the fact that Garleans of all social strata refer to non-Garleans as "savages". The people should be happy that they're continuing their ancient, storied (60 years), tradition of having a ruler from the family that has tried to varying degrees of success to kill their own people three times before, but the fourth time must be the charm.