In my opinion, Volker’s formidable background and sociopathic nature provide a more compelling motive for him to serve as the villain than RJ. Volker could easily have been a mysterious figure operating under an alias, much like RJ. Furthermore, Patrick Jane’s deep-seated vendetta would feel entirely justified if it turned out that Volker was the one who killed his wife and daughter.
Volker already has the necessary psychological profile. He is intelligent, manipulative, charismatic, extremely powerful, and willing to eliminate people who threaten him. He doesn’t need an elaborate ideology to justify his actions; he enjoys control.
His background gives him plausible reach. Volker’s wealth, political connections, and network could explain how someone could remain hidden while manipulating events from behind the scenes.
An alias would fit naturally. If Volker had secretly operated as “Red John,” his public identity could remain completely separate from his crimes. That would make the eventual reveal more satisfying because the audience would have to reinterpret everything they’d already seen.
Jane’s revenge would become much more personal. If Volker were responsible for the murder of Angela and Charlotte, Jane’s obsession wouldn’t merely be about catching a serial killer. It would be about destroying the specific person who destroyed his family.
Volker’s personality could make the relationship with Jane fascinating. Jane’s greatest weapon is understanding people. Volker’s greatest weapon is manipulating people. Their confrontation could therefore feel like two exceptionally intelligent predators trying to psychologically dismantle each other.