I posted this once before... I'll do it again...
Change Dante's move system to match Vergil's. Instead of angel and demon 'weapons' (Which all come from demons and it really makes no sense to get an angel weapon from a demon.) Give each weapon an angel, demon and human mode. That would triple the possible moves for every weapon. Imagine, Eryx In heavy mode is all heavy punches, in angel mode is all fast kicks and in human mode is one button for medium punches and combos, one for medium kicks and combos like usual. A similar system for every weapon.
Cycle through heavy weapons with right d-pad button, speed weapons with left d-pad button and guns with top or bottom button. Also, if manual lock can't be done due to the awesome angel/demon button layout, allow for hard lock by clicking in the right stick Ala Darksouls (friggin' love that game) It's not perfect, but nothing really is and it would allow me to keep a bead on singular quick enemies as they dash about.
Also, ditch inverse rainstorm for twosome time or some other gunslinger move.
Taunts... Just...Taunts. Do it... Put them back in the game.
Also, charging guns and THEN hitting a style button will allow you to perform a stylish gun combo akin to Dante's moves in Marvel vs Capcom. Something- Anything to make the guns more of a center piece to Dante's arsenal as one could almost forget they even existed at times with how little love the girls got in both the game play and cut-scenes compared to previous versions of the character where the guns where always his first choice, a lead-in weapon before pulling out the Rebellion.
Also, enemy specific grapple moves. I like the idea of double tapping the Demon pull or angel lift to perform special moves ala Nero's buster. Expand upon this to include super moves on the bosses as well and make the moves all unique to different enemies.
More in-between and character specific identifying animations. These are the cancel-able trailing animations that follow a button press like a sword swing or Dante casually twirling his guns after firing a ricoshot (Did you even notice that) or the way he'd stumble after a heavy swing of his sword. Just like old Dante would say "Adios amigo" and casually kick Pandora up to his grip playfully after firing the omen in DMC 4.These are how animators instill character in the movements of the avatar on the screen so it's not just 'any' sword swing or 'any' gunshot or a run or a jump or whatever. It's done in a way that makes you subconsciously think "That was Dante's swing, run, jump, gunshot, or special move." Every move and animation must be stylized in a way that coveys character. This game was sorely lacking in that regard.
Also, Metroid-vaina style exploration. Give us a large area to explore rooftops to sewers with area specific enemies and unique ambient music and feel. We don't know where to go next as the game won't chapter skip us to the next area and we can backtrack to whatever area we wish to farm for orbs or just have fun or whatever. In fact it would be helpful as you could recycle certain areas as is the nature of hub based game-play to revisit past areas of the game from new places as all areas connect via the hub. This style of game was used in the first DMC and Ninja Gaiden and really gave a real sense of exploration and lived-in tone to the game. In the beginning of the game they just showed you this dark scary game world and said: "It's yours to conquer. Inside there are secrets, power-ups and many-many enemies all lead by uber-strong bosses. Good luck." And you saw the scale of the area you'd be infiltrating as you approached from a distance.
Also, more personality, less attitude. Stop telling us how "underground, vulgar and rebellious" Dante feels- we get that- and start showing us who he is. 'Angry' is not a character description, It's an emotion. Like all emotions we experience several of them during the day. We're supposed to like being with this guy-I mean we have no choice- give us a reason to like him as well as care about him. I was invested more with Vergils' story because he wasn't trying so hard to prove anything. He fought against the darkness inside before giving in to it. He had something to fight for and he did it alone. He was in pain, dying even, and his story had him fighting back from the brink, finding himself, gaining strength and rising up all on his own I might add(he never had a brother to guide him and tell him where to go next). Vergil had real personal passion as well as flare and when it was all over he was very clearly and unambiguously a different man, not just the same douche with a different agenda, and it came across better to me than Dante's story did.
Also, why wasn't Dante cheesing and laughing with Kat after defeating Mundus. The fact that they were happy it was all over and Vergil was focused as if it were just beginning would have been an ominous contrast easing us into the shot to the chest that was his reveal. In fact Dante should have been a more positive character overall in the face of demonic rule, a bright spot in a dark world that contrasted his brother's colder, more serious focused tone. A light that the previously morbid Katherine slowly gravitates towards as the story progress showing her ascent from the cold darkness of her past into the light of the promise of a new future that this brash devil-may-care punk represents. Further conveyed by the removing of her hood and full reveal of her face for the rest of the story. Dante should be less intense as that is a trait of Vergil. He should be serious only when the life of Kat is at stake and he breaks free from his brother's command to take control of his own path.Instead, Dante was far too angry and tough-guy violent revenge machine for me.
Levity... THE STORY HAD NO REAL LEVITY. The overall story seemed drab and morbid and when it was trying to be funny, it came across as either sour, vulgar or mean spirited. Even the abrupt, gray, downer ending giving no levity to balance out the darkness. t should have ended like the last two games as the demons are now shown to be revealed and roaming free on earth after the destruction of the hell gate, Dante is surrounded by them and alluding to his future as a demon slayer eradicating this vermin from the earth as the closing cut-scene ends in him charging the demons with a cocky smirk. As the credits roll we get to play as Dante protecting Kat From the horde.
That's all I can think of... For now.