damn. that's a really good theoryI still think he's a great demonic entity disguised as a businessman, however his true form has been sealed by sparda within limbo and mundus needs Dante's blood and amulet to release his true form. That would explain why all the demons are trying to capture him. I also think that mundus was able to capture vergil but the latter faked his death and escape which would explain why the voice in the demo said that "Mundus doesnt know I exist"
And yes that voice is vergil.( I really hope so)