^Speaking of the "original eight" (9, actually), I think they should find a way to make Vincent and Yuffie mandatory and not optional, they're just too important at this point.
Ignoring the the compilation you could get away without Yuffie, but I don't think Vincent's part of the story had any right being potentially left out in the first place anyway. You could still leave Lucrecia's cave and stuff optional if they like, you can get the gist without it, and otherwise Vincent would have the only mandatory-to-access ultimate weapon.
As for Aeris, who are you kidding Bedford? We all know SE would just release a post-death playable Aeris as a $20 DLC.
On the topic of the Compilation and optional things. I don't care if they go hog-wild in putting things in connecting the game to Compilation entries AS LONG AS THEY ARE ALL OPTIONAL. Don't touch the main quest at ALL, all your Compilation stuff was to fit that, not the other way around. So if you leave the main plot alone but throw in the Modeoheim ruins is an optional endgame dungeon I am totally cool with that.
and have Cloud tell Zack's parents what happened, that asshole