The biggest problem with King Bran is "then what?" He can't produce heirs, his closest relatives are Sansa, who is busy being Queen of the North, Rickon (MIA or dead as far as anyone knows) and whatever cousins or nieces/nephews come out of the woodwork and decide they want the throne he's on, and barring them whatever is left of the other houses a generation later. Instead of looking towards the Wars of the Roses for inspiration, we'll be looking towards the Hundred Years War.
I'm pretty sure the ending with Sansa becoming Queen in the North put the Iron Throne into electoral monarchy. So whether or not Bran can have kids is not the question; the moment he dies, the nobles just go full Holy Roman Empire/Polish-Lithuanian Commonwealth and elect another monarch.
Yep Joffrey and Tywin Lannister can’t keep getting away with it…
Joffrey and Tywin weren't killed because they were evil, they were killed because someone else thought they were in the way. Tyrion sought vengeance, not caring at all that killing his father would de-stabilize the realm, and Joffrey was killed so that the nobles like Littlefinger and the Tyrells can have a more pliable puppet in Tommen.
I hate GRRM's writing style and what it has done to all types of fantasy. (Fuck everyone who was responsible for FFXVI "the GOT of the series".) I will give him credit the red wedding and Robb's death was good. To give the show runners some credit too Stannis burning his daughter and STILL losing was also good. He can write/setup some pretty good downfalls.
Stannis' death was just them killing him off so Jon can take his place; it makes little sense to me.
I can't even see Robb's death as original. Star Wars beat him to it with Order 66, which was inspired by the Godfather. Robb was just too stupid to politically weigh his marriages and got himself killed as a result. The Red Wedding is just repeating what happened to Ned Stark to his entire family.
Although if this were the realistic Middle Ages, he'd just be under house arrest in KL, where Tywin can keep an eye on him and his mum. Especially since Tywin is on record as wanting to create a good legacy for his family that can last a millennium; killing nobles and royals is the last thing that can achieve that. If you keep doing that, no noble or royal will make deals with you, and the Church would excommunicate your ass. Especially when your guys kill baptized royal babies.
The problem with GRRM is that he passes off ASOIAF as realistic to the Middle Ages, when in reality, too many people don't give a shit about religion, and they're way too eager to spill noble or royal blood, which is something the medieval people are not. More than likely, the enemy lord or king will capture you and sell you back to your family for every red cent in your family's wallet. Like how Richard the Lionheart pissed off some German dudes during the Crusade to the Holy Land, so they captured his ass on the way back and forced the English to pay a huge-ass ransom for his return.
They also had female knightly orders, so Brienne would have a place to join. The ban on female knights was done in the Renaissance, long after the Middle Ages.