Dante has made a bold claim to serve as humanity's protector, the human's true guardian. His brother Vergil is gone, for now, plotting in the background his own maniacal scheme for power to rule supreme.
Dante would assist Kat in finding other potential followers to aid his cause, and they rally up a team calling themselves The Order Of The Sword (Taking the name from DMC 4) This could introduce Trish as a demon who had a change of heart, like Sparda did. Lady, whose past is like Kat's, except she's half human and half demon because her father sought to becoming a demon and then raped her mother to give birth to her when he was one.
Now you have a small team of fighters against the demons running amok. Except now with Mundus defeated the next strongest demon in the Underworld will take over from Mundus, and despite his imprisonment that is now Sparda.
Sparda after years of imprisonment, releases his rage and slays a vast majority of his own kind. The only problem is that he has gone completely insane and thinking he has nothing worth having anymore since Eva's death, sets his heart on destruction and chaos. He's been driven to complete madness and grows to become an unstoppable and unrelenting God of destruction.
The Angels who have turned a blind eye to humanity since the demons had spent an eternity brainwashing them and tempting them to sin, now turn their sights to humanity in the wake of the demon uprising.
Their most elite warriors descend down to attempt to put a stop to the evil and instantly sense an unwelcomed presence. Dante, a Nephilim, is despised by Angels due to his blood being impure. They hate the fact that an Angel would side with something as foul as a demon and disregard the idea of love being the cause for that.
So, Dante has an enraged Demon God waging war on everything, that happens to be his father. A group of powerful, elite Angelic warriors. And a scheming brother to deal with.
That's how I'd like DmC 2 to go. I'll explain more as to what I would do as Dante etc soon.