Guys, I have a theory: Remember when Sargeras heard about the Void Lords, and their plans to corrupt a Titan into void, which is said to corrupt the Universe in eternal torment?
And we all know that Sargeras is EMPOWERED By the Fel (AKA, twisted). However, I have a theory. What if....Sargeras wants to turn Argus into a FEL TITAN?! Ya know how Void Titans have Old Gods on them, and such? And you know how Void Planets are all purple and such? Well, on Argus, we have Sargeras talking about the Re-birth of the Pantheon, you have Demons talking about the "Process", and how "It's already begun". I don't think that said process, and all talks about the Pantheon, I think it's something more.
I think Sargeras wants to create his own Fallen Titan, but Fel infused. Argus' description alone talks about him "Rising", and being told to "Begin the end of all things", and his body has no skull, stitches, and so forth all around him. Argus also looks deformed, and held together. Even though Argus might not look fel-infused, it is likely that he is a Fel Titan.
Maybe this is Sargeras C Plan all along. If the Legion didn't work, than his Dark (AKA, Fel empowered) Pantheon would. And if that didn't work, than his Ultimate Weapon that can easily destroy the Universe could, AKA...The Unmaker. Sargeras' very own Fallen Titan.
While Sargeras tries to destroy Azeroth, Argus may try to Destroy the universe while we attempt to stop his process. If a Void Titan alone could make the Universe its own playground, then Argus could turn the Universe back to what it was before flaw began, AKA...NOTHINGESS! Unmaking what was once made, back into the first step of creation: Light, and Shadow.
This is just my theory, though. I'm likely 500% wrong on this. But, we do know that Titans are very intelligent. And Sargeras is no fool, himself. Hell, Sargeras didn't want to destroy Azeroth when he saw her, either. He wanted her to be on his side. However, there's only so much Time, and Sargeras already sense enough power in Argus. So...why not?