Environments: We already know Niflheim's in there, looking prettymuch the way it did in FFVII, so I'd like to see Mt. Nifl and Lucrecia's cave return in the same regard. The streets of Junon in a nighttime setting would be cool, too.

Music: I want to hear refined versions of "The Beginning of the Nightmare" (Vince's theme), "Anxious Hearts," and "Trail of Blood," and maybe a brooding remix of the FFVII main theme.

Gameplay: All of Vincent's original transformations should be implemented in addition to some new ones, but Chaos should remain the most powerful (except, of course, for the super-secret "need the strategy guide to figure out how to get it" ultimate one). Materia should at least be applied to his weapon, if not his armor or accessories. Non-FFVII-fan-service-wise, it'd be nice if he could grasp or tear at things with his claw-arm.

In general, there should just be a consistent flow of clever references to FFVII throughout the entire game, from character appearances (like Cait Sith, but also by minor characters like Zangan) down to passing allusions to issues and events raised in FFVII. (Random Niflheim townsperson: "Hey, remember when the town was just filled with crazy mumbling invalids draped in black cloaks? Was that crazy or what? Haha OH SHI--*Lost Number II smashes through a wall, start boss fight*")

It'll also be interesting to know what happened to Niflheim's citizenry ever since Shin-Ra, Inc. crumbled and the actors stopped getting their paychecks.