Yes. Vergil dressed in a red coat, styled his hair like Dante, took Dante's voice, adopted Dante's cocky personality, replicated or stole Rebellion, Ebony and Ivory, abandoned his whole beleif system and decided guns ain't such a bad weapon for a true warror after all, oh and he made sure that when using Ebony and Ivory, he held them cross arm style, besy way right? It all sounds exactly like something Vergil would do.
Look I'm sorry man, but if it looks like, sounds like, and moves like Dante. 99% of the time, it's Dante. The other 1% of the time, it's usually Vash the Stampede.
It is indeed a crazy thought, but no, it would NOT be a very good story for DMC4. It's the kind of story which would make me seriously consider flying to Capcom Japan HQ, attaching a bomb to myself, and unleashing some explosive justice.
PS: If I seemed overly harsh, I vaguelly apologise, I generally post on much more harsh boards, and this is the kind of reply I am used to giving.