Re Aegon and marriage alliances, what specifically would you have advised him to do differently? It doesn’t seem like Tywin’s opposite approach was much more succesful

He absolutely needed to make his children comply with these marriages. Whatever it took – whether that’s fostering his kids with their intendeds so they grew up around them (and not their own brothers and sisters who they wanted to marry), whether that’s assuring them sotto voce that once they get married and pop out an heir they can have all the paramours they want, etc.