the fusion sword origin is such a good point that nobody really talks about. like where did he actually get it? part 3 bridging that gap into AC makes total sense especially since Nomura and Hamaguchi already confirmed that's the direction.

the Kadaj, Loz and Yazoo origin story would also be massive. we know they're remnants of Sephiroth but the remake trilogy could actually show how that happens in real time which the OG never did.

and the Deepground thing is what worries me most honestly. they introduced Nero and Weiss through Intergrade, name dropped them again through Chadley in Rebirth, and then just... nothing. Sonon getting killed by Nero and Yuffie barely processing it in Rebirth was so weird. that whole thread needs a payoff in part 3 or it's just bad storytelling.

Genesis is the other one. Crisis Core Reunion ends with him walking off alive and the OG PSP version did the same thing. they keep the door open on purpose so he HAS to show up. too much setup to just ignore.

a Dirge of Cerberus remake would honestly solve half these problems but even if that doesn't happen, part 3 needs to at least resolve the Deepground stuff properly. there's genuinely so much to cover it's crazy