Hmm even if they didn't bring him back in a gameplay sense, id still love if they did something like what batman arkham knight did with joker, just have V randomly show up and give his thoughts on what vergils doing maybe? That would be a cool contrast on how the two are different.YES!!!!!!!!!!!!!!!!!!!!!!
Him being Vergil's humanity is a waste of a good idea. Ironically Nero being a younger Dante would feel more believable. V and Nero have the opposite problem (he feels too reminiscent of Dante while V felt too little of Vergil at first).
PS. I'm biased- V rules Nero drools- NO REGRETS!!!!!!!
Outside of a flashback, he's just gonna pop up as Vergil's conscious or an alter living in his head with Urizen.
Right now I'd settle for a Summoner style in a future Vergil game and Visions of V starts being more daring with its material. Or a DLC where V wanders around during the month in between the first two levels and stumbles upon a place Vergil visited.
There's always an alternate universe but that feels too much like a cheat.