I would've liked to see Genesis. They didn't have to give him a whole story section, he could've just shown up as an optional boss in Olympus Coliseum like Sephiroth did in the first KH. I imagine the scenario two ways:
1: After beating the Final Episode, you return to Olympus where Phil tells you there's this new guy dominating the Games and scaring most of the competitors away. He asks you to beat this guy for him and you agree, heading in to fight him. The area is darkened (Like during the Ice Colossus battle), the giant symbol for the Apocalypse Spell (the one shown when Zack uses the DMW attack in CC), Genesis warps in through the portal (Burst of light, waves of Darkness, a simple graceful landing...take your pick) with his back facing you. He extends his wing, then turns around, giving you one of his smiles, and takes a fighting stance, prompting Terra/Aqua/Ventus to do the same. Then the battle rages on (Keyblade Swing, Keyblade Swing, Black Flurry, lengthy sword combo, Spam OHKO move, retaliate with Payback attack...yadayada). After beating him you see him kneeling on the ground. He smiles, stands up, and says "Give my regards to Zack...", then vanishes in some extraordinary method.
2: Adding a bit more to the storyline, it starts off the same as 1, but with cutscenes instead of a dialog bubble. Zack runs in hoping to enter the next games, and overhears the conversation. The ever eager "Puppy" he is, he wants to investigate with you. Instead of dim lighting, it's still daylight in the Coliseum, and when you and Zack head in, you find Genesis waltzing around the battle field spitting lines of LOVELESS from his mouth with an Apple in hand. Zack recognizes him, the two exchange a few words, and everyone takes a fighting stance. In this version, Zack is your ally, so you've got a helping hand. After the battle, there's some more dialog, Genesis tosses the Apple to Zack as a memento of your victory, then leaves, puzzling everyone.
In either version, you receive a cool Genesis-themed Keyblade (Called Goddess Materia or something like that), and you can rebattle him without the cutscenes anytime afterwards. His battle music could either be "A Beating Black Wing" from CC, or a KH-ified version of said song.
What do you guys think? I think it would be interesting either way. There doesn't have to be a reference to anyone else in FF7, just Zack and Genesis.