I think this campaign would benefit greatly from all-new sound design. New music, ambients, interior and exterior sounds, might be even new NPC voices.
I remember how T2X astonished me with its complete sound overhaul, from footstep sonds to new conversations everywhere - it made it feel like another original game, and not a fan campaign. Hell, I do consider it another original game.
I'm already sure that gameplay and level design in The Black Parade will be top-notch, but how great would it be to go further and bring this project to the level of T2X in originality.