I was thinking about the Kuriotates, how their multiracial society has currently got just 3 members (and that's if you count Lamias), and how perhaps ogre-sized trolls (or some sort of giant) could replace the War Elephant for them. Trolls are just about the only major fantasy people not in FFH that don't violate the princess rule
Not even close. Assuming each hit with every attack, a troll does 1 less point of damage than a stone giant on average. But the giant has 1) a better attack bonus and 2) Power Attack. A hill giant also has a better attack bonus and Power Attack, so it will also deal more damage on average than a troll (especially when you remove the assumption that each will always get a full attack and hit with all attacks).and possibly starting with the shock promotion to represent their insanely high damage output in melee (outstripping that of any other Giant (stone, cloud, fire or hill) or an adult dragon of any variety)
Technically, they've got five: Humans, lamias, centaurs, either elves or dwarves (depending on religion), and dragons.
I agree, though, that they could state to be more racially diverse.