While typing my response to the other DMC5 wishthread, I started thinking about this. I like to come up with plots and stories even if I stopped writing them down as fanfiction a long time ago.
So bear with me if this is totally ridiculous but I like brainstorming stuff like this even if its never gonna happen.
For some reason I started thinking of Trish. Eva was long dead when she walked through the door looking like her twin. She was created that way on purpose to lure Dante into a trap.
Dante walking into traps seems to be a running theme of this series. So, why not give him another one. Only this time we'd all know its a trap because it's Vergil who busts through his door, demanding the return of the Yamato. (With or without lugging a motorcycle at Dante's head, of course.)
Obviously, it can't be the real Vergil. Created then, by someone hell-bent on opening that gate again, like they always are, and wanting to get rid of the only person they figure can stop em. After the 'brotherly reunion', back in Fortuna city, Nero gets confronted by this Vergil bait too and is in the process of getting his ass kicked by it when Dante shows up to lend a hand. Thus begins the game, with a WTF Vergil?! prologue and the legend and the rookie starting off together to investigate.
So here's where my idea gets the weirdest. Heh.
Assuming that Yamato is possesed by the demonic essence of Vergil's spirit - as it seems to be hinting at, what happened to the human half? Like one of those residual hauntings or whatever you see on Ghost Hunters, what if it clung to something as well (his half of the amulet perhaps, I mean what happened to it? Stolen? Lost? Trish was supposed to have it but... it hasn't been seen since the first game.) Anyway, whatever it is, this Vergil bait was created from his human essence. It's weak, of course, and corrupted - but when it comes in contact with the Yamato and the other half of his soul...
Well who knows what could happen, then, eh?
Anyway, as far fetched as it is, if it were a book - I'd read it! :3 They could make it believable, right? X)
Still, I'm not sure if bringing him back whole would be a good move for the series or not. As much as people want him back, what happens next? Maybe he makes a better plot piece (as mentioned above) if he stays dead. But its fun to think about, nonetheless.