The nation has to have one central governing authority. Has to, otherwise there’ll be endless war. No doubt Martin is using history to critique the idea of a monarchy or a ruling class, and often in this story the best characters are the lowest - Davis, Sam, Varys for example. They’re his true heroes, that’s his underlying message. That the weak and fallen and leaders are the best of them all. More superhero geek fulfillment stuff (which I’m guessing somewhat accounts for the series success).
This story is about the current protagonists fighting for the throne, to ultimately continue the existing structure. And giving what we’ve been shown that would be a bad idea. But to move to some sort of representational democracy would still be a big step. An elected council for each of the seven kingdoms. I don’t think despite all the war that Westeros has learned to go to a new model. Plus you have a massive change in fortunes and property. And the rabble from what we’ve seen of them seem to be utter shits.
So I don’t see how this story ends well.