Ok...
I think I know how to make this sequel work. It won't be for everyone, but it'll have to do.
More Weapons:
Bayonetta and Ninja Gaiden II had a lot of weapons. In fact most of them were actually sort of similar to each other (except for the fact that Bayonetta had bullets shooting out of her melee weapons, but that's a different story altogether).
I know this sounds bad, but DmC2 should just take some of the weapons from those games.
I know that it's argued that quality should remain a higher priority over quantity, but increased funding may help in that regard (you'll see that funding will pretty be my "solution" to almost every problem that making the sequel would bring up. I have no imagination, I know).
Zelda exploration:
You'll find that a lot of my "improvements" are ideas taken from other games. But why try to reinvent the wheel? We're just trying to make it go faster. I say, let the entire game take place in new version of Limbo, that way any level inconsistencies can be explained away with, "The world is a creature of chaos" (Castlevania reference)
Combat:
Add a lock on function for those who want it. I noticed in a review someone posted here (not the one I posted, but another one) that the lock-on function could have been turned on and off using the down button on the d-pad. I don't know if there's any truth to that notion, but it's an idea worth exploring.
Either that, or just bring back the hard lock-on. No sense in keeping the current targeting system if it didn't work as well as it could have.
Bring Vergil back (again).
Vergil will most likely come back as Nero (not Nelo, that was a typo) Angelo. Although Ninja Theory could just take the unimaginative route and call him "Dark Angel". Who knows? Once he comes back, he'll most likely be driven mad with the pain of defeat, and the overflow of newly-obtained power in his system. This time, he should be a final boss that's
truly worth remembering.
Sparda:
Have him make an appearance. Then, maybe have Vergil cut him down out of anger overconfidence, increasing the stakes in the story. Sparda should put up a good fight, but must rely on Dante to save him in the end.
Yes, I know that this is something most people won't like, but it's just a way of showing how powerful Vergil is this time around. And what better way to demonstrate it than by taking down Mundus' former right hand man?
Framerate:
Do I really need to get into this? Sing along if you all know the lyrics.
"We need 60 fps to maintain fluid action gaming bliss. Make it happen"
Taunts:
Taunt prompts on the screen play out prerecorded dialogue. Not very creative, but it's the only way to keep narrative consistency.
Besides, there are a lot of other ways to bridge combos other than taunts.
Style Meter:
Two options: Easy Style Meter, or Difficult Style Meter. The player should have the option to choose.
Devil Trigger Enemies:
Bring them back, NT. "Damage-sponge" enemies build character.
Enemy A.I.
More aggressive. Especially on DMD.
No more color coded enemies.
In DMC3 certain enemies had weaknesses towards certain weapons.
But they could still be taken out by other weapons as well. Seriously, keep that system. It works.
And finally:
Dante Will Die Mode. Yes, I'm serious.
If you don't like the idea of that mode, then just leave it alone. That's something only for the truly masochistic, anyway.
In conclusion:
Fix the flaws of the first game, and the fans will follow.
Edit:
Make DmC2 the final game in the series:
After fighting a powered-up Dark Angel (Nero Angelo), there really isn't anyone else who can present a challenge to Dante. It should end there. The skeptics will be happy, and the supporters will be satisfied with a good ending.
After that, Capcom can go back to the "classic" series and have Dante fight the Tooth Fairy, because that would make about as much sense as DMC4's story anyway.