A bit of a hot take, perhaps, on book 9's dropped potential.
So... I know some people dislike book 9's ending for being a bit goofy. "Haha we tricked Visser 3, told him grape juice instead of tomato juice".
Which, I get, but also they are kids, I could see them pulling a stunt like that.
But to me, the biggest issue I've got with it is that I feel like there was potential, later in the series, for them to end up in a situation where they want to compromise with Visser 3, and he refuses, on the basis that they've broken compromises and deals like that in the past, bringing up that incident. Leading to actual consequences.
I feel like it would fit really well with the message the series is trying to portray, and would take a silly one-off moment and give it surprise weight later on. Because genuinely, that is what happens: you break deals, people refuse to make deals.
I don't know, just a simple thought that was in my head throughout my reread.