Really solid idea, but it could really use some mixing. The vocaloid patch gets lost in the mix and the big moments get pretty muddy. You'll probably want to roll off the high ends of the strings. And put in some sidechaining for the drums, they kinda lose their impact in there. Also you really don't want to be cutting the master fader down during production, it'll give you a false impression of how it's mixed. I usually try cutting instrument faders so the master comes out to -10db without having to mess with it. Leaves plenty of headroom and lets you know more clearly how everything is mixed.
Still a fantastic idea, I can't wait to see what you make of it.