Kirby's reveal
It would've been hard to keep secret, but I wish that when they shot 4, they'd had more forethought to shoot footage of Kirby's survival, could've been used as a flashback to illustrate.
Also, there's always the rumors of Stu surviving. It'd be cool if they'd have transferred that to Kirby somehow. Like, all these years, she was alive and in hiding, but there were varying accounts on whether or not survived in 2011.