I actually like everything about DMC2. The dark, cold style of Dante is, fair to say, out of the box compared to his earlier forms. I admire reaches in different directions.
But from playing all the DMC games, I'd replace Lucia, give Dante the same charm he had but with less words, bosses dialogue so they can mock each other and possibly give some back story and an actual, proper climax at the end instead of a cliffhanger. I hate cliffhangers with DMC games, I resent how they didn't finish off 4's plotholes.