You know, except for the stuff where Ramza clearly develops and progresses as a character, like learning to face trials and responsibilities head on
Yes, he really does a good job in Chapter 4 of living up to the duty that his noble status requires of him. Except not. Family is important to Ramza, but he doesn't care about the duties of his station, and we see that back in Ch1. So what is there to keep him in Ivalice?
Lategame Ramza clearly looks out for his sister as a top priority, and other people in general as a strictly secondary concern. Consider what he does and doesn't do with the Germonik Scriptures. At the end of the game, if he and Alma are alive, then they have just barely escaped being killed by the Lucavi through a holy miracle, plot hole or what have you. It is entirely in character for Ramza to say "I'm going to protect Alma, the rest of the world can go hang". He's already done it more than once.
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I don't like this duchy. Now, it's an adventurer.