#26 from the Ellimist's perspective would have been fascinating. Or #48, from either Crayak's or Drode's. Or David's, for that matter.
AC, from Arbron's perspective, or Alloran's. Maybe it's just that I wanted
something from Arbron's point of view. He didn't get nearly enough written about him in the series.
Oooh, or how about #33 from Taylor's point of view? Either the Yeerk, or the human, either of them would have been fascinating. All of her character development came from what Tobias thought of her, and you have to admit, he's probably just a leeeetle biased on the subject.
#10 or #53/#54 from Erek's perspective would have been interesting. Erek was another character who, for how major a character he was, kind of got short-changed in the character development department.
Seeing something from Aftran's perspective would have been cool, too. Like, what she was thinking when she decided to become trapped as a humpback whale.
Fanfic writers, are you guys taking notes?
And, of course, I agree with everyone who has said that Tobias and Ax didn't get enough books. It was so unfair! They're my two favorite characters, and they both got gypped in favor of the boring stupid human characters!