Oh yes, I like it! I thought of similar scenarios after the E3 trailer. :oI like this post and decided to come up with my own fanfic. I came in with the idea that I would want to make the least amount of changes with the largest impact that hit on what I consider the game's greatest weaknesses. In order to this, I would change two things:
1. Vergil does not split himself for some lame, "I have to be stronger," reasoning. Instead, he sepearates himself because of the fact he is weak/dying after being free of Mundus, and he believes it is because his demon-half can't survive any further without Mundus after what Mundus did to him. He splits himself to at least survive, and only realizes afterwards that it was his humanity that was dying and that he fucked up. Or something like this. I like the idea that the split was for survival's sake.
2. Vergil comes to Dante as---PLOT TWIST---Vergil. Weakened, human Vergil. And he comes to him because he needs help merging himself back into one. One of the biggest disappointments of the game is that we have few nteractions with Dante and Vergil, and when we do, it boils down to sibling rivalry silliness. I enjoy the rivalry! I love it! But we needed more than that. To have a full game with Vergil's weak ass tagging along, being able to converse with Dante and Nero, gives us so much opportunity for juicy scenes. Emotional, funny, whatever. This can also lead to a tragic ending. As Urizen absorbs more blood and grows in strength, Vergil can voice fear---when they were one, they were both a side of a coin. Equals. With Urizen growing so strong, and Vergil only weaker, would Vergil be able to control himself when they became one ? And of course, for drama, when Vergil does merge back with Urizen in the end, he can't. Not that well. So when Dante and Vergil do fight in the end, it's real. It's not a joke. It's not pure sibling rivalry. It's a Vergil who has to finally reconcile the hate (the demon) that has grown even stronger inside of him, which has it's focus on Dante. And only his son stepping in at the last minute can break Vergil from his hate. (And in order for the Nero moment to work, Vergil shouldn't know Nero is his son until this ending scene).
(I also had the idea of V being some regular guy, who is instructed by Vergil from behind, but that's not usable anymore.)
I'm still struggeling with lots of things, but for now I'm going with this background:
At the end of DMC1 the Nelo Angelo armor explodes and the amulet's chain breaks. That's what Dante sees and thinks him dead. But his real body lands somewhere in the debris and is washed into the sea when the island crumbles. He is washed ashore somewhere after some time, barely alive.
Although Mundus is sealed again, his old curse isn't gone entierly. Vergil has no memory of nothing, just wandering around half dead and tortured by nightmares. Over years he starts to remember things. He then comes close to Fortuna by chance (prequel novel says, Yamato was washed ashore there. So it should be not too far away from Mallet Island, and Vergil could end up in that region as well.) and start to sense Yamato. He observes Nero for a bit, he has no idea what's really going on, and then just walks in and takes back what is his.
Now the sword gives him a lot of memories back the good but also the bad ones. The corruption eats further away on him as well. He goes back home to die where Eva once lost her life for them.
He stabs himself with Yamato to silence Mundus's corruption, to get it out of his body. He can't stand the voices in his head anymore. Just make it stop, even if it means to die. He didn't expect to separate himself like that.
Now his remaining self needs to take actions against that demon part of him, that is still corrupted by Mundus. So he seeks Dante's help.
I'm not sure if he hides his indentity or reveals himself. I'm leaning more towards hiding, because they act so distant in the game, it kinda hurts. (One thing why I struggle so hard with thinking Dante knew the whole time V is also Vergil. He is so mad and pissed at him. :/)
V tells Dante about corrupted Vergil-Urizen, who completely lost his mind to ensure, Dante is ready to kill his brother. Dante uses Jackpot to test if it really is Vergil, like he was told and maybe, how far his mind is really gone. (But I still have to ponder on Dante's hostile actions in the game in general.)
And then I would throw all this "mother abandoned me", "what if we were swapped" and "look, a son!" stuff out.
Also still working on what V and merged Vergil are really after. And how did V know about his demon side using that tree? How did he find Morrison? (Why not go directly to Dante?)