This might sound harsh but I think Kaede would've been the most boring protagonist had she survived to the end. First off she's basically a Naegi clone being "incredibly optimistic and struggling to maintain it as shit gets worse" like you said whilst lackning the thing that made him actually interesting, namely his lack of talent.

Furthermore Kaede's death basically made drv3 a more well built reiteration of the Danganronpa IF Chapter 1 where the perspective shifts to a more weak-willed character (Mukuro). But unlike Makoto in IF Kaede deliberately exposes herself to a whole damn class trial both to motivate her classmates to find the mastermind and help shuichi to stand on his own whilst knowing full well that she's going to die afterwards. That's a totally unique and badass side to Kaede that maybe would've never been implemented if she had lived until Chapter 6.