I had this idea for DmC 2, where Dante is on a mission to get help from the angels and there’s a train that kind of travels between the astral planes of worlds (Phineas informs him of its existence just after the events of DmC) The only way that Dante can “reach” said train which carries human souls for judgement would normally be if something like a sacrifice was carried out, but Kat manages to tap into it by her ways as a Medium so nothing like that is needed and Dante is able to board it as it’s heading for Purgatory (Basically an Angel version of Limbo that exists between the human world and Heaven) And I thought it’d be cool to have the carriages separate when he’s on there where you have to demon-pull and angel-glide through to the next carriages. When you get to the front of the train there would be a boss and after killing them the train comes to a crashing halt and you’re in Purgatory. Dante is seeking out help/answers as to why the angels aren’t doing anything about the demon invasion on Earth following straight after the events of DmC.
He realises that angels weren't necessarily unable to do anything about Mundus, they were simply turning a blind eye to save themselves from any trouble from him and they had made a deal with the Devil (practically a truce from both sides) So Mundus proceeds to enslave humanity, instead of going about destroying it. That way the angels stay off his back, as well as they simply didn't care enough about protecting humanity they cared more about their own divinity and if humans were to be sinful as they could be then they weren’t deemed worthy of saving and only pure souls would be allowed entry into Heaven’s Gates. It's not like Mundus was roaming around slaughtering humans on a constant basis, just controlling them through debt and mind control substances etc. Yes he was a very bad influence on the human race but ultimately besides the temptation he placed on humans he wasn’t decimating the Earth and humans still had their own free will somewhat so not every action/decision on humanity was soulfully determined or controlled by him and that was good enough for the angels to look past whatever Mundus wished to impose onto humanity.
Dante comes to see that this "peace" or agreement was enough for both demon and angel races, until Dante and Vergil had disrupted it by killing Mundus and ultimately collapsing Limbo spilling it along with its demons into the human world and the angels and demons now see Dante and Vergil as both responsible for Limbo's destruction, and subsequently the demons flooding into the "human world". Therefore to them the events of what happened in DmC are entirely Dante and Vergil’s fault and the chaotic apocalypse that has followed is down to them.
Furthermore Dante begins to learn more about himself and his race through discussions with the angels and also further information about Nephilims from Phineas. He comes to understand that Nephilims have the ability to freely enter into both worlds, the demon and the angel ones. As well as use both of their powers in either worlds to which he can understand why angels and demons would both fear him and consider him a threat as neither demon nor angel can use their powers inside their opposing worlds.
Since the end of DmC, Dante has vowed that he will protect humans. He now views himself as humanity’s protector and its savior. His brother Vergil is gone, for now, plotting in the background his own maniacal scheme for power to rule supreme over both worlds just like Mundus did before as the promise of power and control has made him become greedy and blinded to what actually really matters in life.
Throughout the story 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 other characters from the original series such as Trish as a demon who had a change of heart, like Sparda once 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. Obviously they would not have their original names (Trish and Lady) I would probably change those names.
Something else I would also add is a special mission (besides trying to seal Limbo to stop the demons) that The Order has to carry out throughout the game therefore the story doesn’t just simply feel like “Dante and friends stop demons the end”. Because despite that essentially being what Devil May Cry has always been about it’s a bit too familiar of a plot at this point and feels almost dry and empty. The special mission would have its own code name amongst The Order and I’d even have an opposing group of humans that are so brainwashed that they side with the demons or at least support them and they also seek what The Order is searching for.
The mission, as such, could be codenamed “New Origin”. The “special” package would be a child that is very important to the future and lo and behold this child introduced to the DmC series is none other than Nero and that’s how he becomes set up into the story.
I’d also quite like it if they made Kat a playable character. Every now and then have you control her as she has to either unlock a path for Dante to progress through, a secret area for Dante to explore, or simply use her abilities to “cleanse” an area that Dante has cleared of demon activity making it safe for humans or The Order to set up bases of operations and expand.
During all of these events through the game we come to learn that Sparda has broken from his imprisonment and releases his rage and slays a vast majority of his own kind on his way out of Hell just simply out of anger. And the years of being tortured, enslaved and lied to has made him go completely insane (he was lied to by Mundus into thinking he has nothing left anymore since Eva's death and the death of his children) it’s unbeknownst to him that both Dante and Vergil are still alive. So he sets his heart on destruction and chaos as he’s been driven to complete madness and grows to become an unstoppable and unrelenting God of destruction to which he intends to destroy everything in his path and he is purely fueled by nothing but hatred and rage for anything living; demonic, angelic, human or anything between.
After Dante and the gang have defeated enough demons, cleansed enough areas and took up further operations also carrying out their mission “Codename: New Origin” Kat, Trish and Lady have a lead to follow whilst Dante goes to liaise with some angels (having finally decided to lend a hand amongst the ensuing carnage).
Dante finally convinces them he only cares about humans safety and keeping those he loves safe from harm. He isn’t interested in anything else other than helping to protect the human race so they no longer see him as a threat and because his cause seems just they agree to help him put a stop to the demonic army before them.
Following up on their lead, Kat, Lady and Trish arrive at an empty warehouse besides the docks to speak with their informant regarding information to “New Origin’s” whereabouts. This is actually a trap put in place by Vergil and his small team of followers to try and lure Dante to them in an attempt to take him out using Kat and the others as bait (Vergil knows that his brother will not let him carry out his plans without trying to put a stop to them so the only option for him is to take Dante out of the picture first) In the meantime Kat and the others are tied up and kept under surveillance before Vergil forces Kat to contact Dante informing him that the child they were searching for has finally been found and to come right away.
Dante, none the wiser, parts ways with the angels to meet up with Kat who is being held hostage in a room with Lady and Trish (a gun to their heads). Vergil gets himself ready to surprise his brother on arrival. His plan to kill all three if Dante does not either walk away from his fight to save humanity allowing Vergil to seize control of everything or simply kill Dante if he refuses knowing that if Dante fights back all three will die and their deaths will be on Dante’s hands.
Before Dante arrives, he receives an unknown call tipping him off about Vergil’s trap before it’s too late and manages to free Kat,
Lady and Trish before confronting and fighting Vergil. Before the fight properly gets underway, Phineas appears and informs the twins that their father is ripping the city apart. They agree to stop fighting so they can witness it themselves.
Sparda having now returned easily dispatches a majority of angels with absolute ease. A concerned Dante manages to convince a hugely conflicted Vergil that if power and control is what he has been desiring then letting their father lay waste to everything would benefit neither of them. Dante wouldn’t have a world to defend if it’s destroyed and Vergil would have nothing to rule over. Realizing that for either of the brother’s desires to come true they have to put their differences aside to face an even bigger threat. The two decide to head back to The Order’s main headquarters to “gear up” before they head off to put a stop to their father before he annihilates everything and everyone in his path.
A long ass battle ensues but with the help of Phineas they finally manage to get their father to realise who they both are and that they weren’t actually killed by Mundus which causes Sparda to regret his actions that he took and the darkness that he allowed to consume him. He vows to never return to the human world again and between them they travel back to the underworld to close the portal/veil that conceals the demon world from the human world ultimately ending the demonic invasion. Before they all separate he tries to reason to both brothers to put an end to their fighting and work together to make sure that nothing comes between their family bond. Vergil finally understands his foolishness and Dante forgives him before they return back from the demon world and the sunsets on a peaceful Earth now completely demon free.
A post credits scene reveals Dante, Vergil, Kat and the other members of The Order at their main headquarters when the camera pans across to a young child sat on a table next to Dante who is on his phone. He looks across to the boy and says “I guess I should finally change your name in my phone, right Nero?”. This reveals that the child already knew The Order was searching for him and already knew about all of the events of DmC 2 before they all unfolded.
“So Nero. What does the future hold for us all?” Kat asks.
Nero (smiling towards the camera) “Oh, a lot”.
THE END.