I do not completely support this view. It has never been shown that consciousnesses can in fact switch between different people. Sigma always jumps to a version of himself, as does Phi. Morphic resonance is of course a connection and information transfer between two different people, but as you know it does not involve consciousness hopping.
As for the 3 protagonists: I think that has been done because of the structure of the game. There are three teams and they can only communicate with the dog. It would be impossible for 1 protagonist to witness all of the story. That also seems like a logical reason to me.
But Kyle is sent back to help Sigma in ZTD. - It's too long ago, what are the details, I'm sorry if I'm confusing - Still, I wonder if he could just jump to someone else's body. He is a clone, so there should not be any other version of him besides Sigma. Or Q is a child Sigma and we're going that way xD It's so confusinngg. Or perhaps Kyle is the Zero of this game.