Thanks, but that would add a lot of complexity to a story that already has so many elements beyond what's apparent to the reader over the course of most of book one. The first of the true complexity is revealed at the climax, when the basic conspiracy is revealed.
The complexity grows deeper in book two (e.g., Connor sharing the soul of Adam, the beginning of end time disasters, the identification of an incoming comet that will eventually destroy all life on Earth, incorporating other religions into the story (although not in a huge way), Connor learning about the genetic breeding that enslaves him to Satan, the attempt to retake the Vatican, and so much more).
The most complexity is in book three (more end time disasters, the rescue mission into Hell, Connor deviating from that plan, the confrontation at Armageddon between Connor's forces and Satan's, the return of Christ, Connor finally having to settle the Last Challenge, Connor potentially having to throw himself into the lake of fire to save others, eventually being taken to the top of a mountain to meet God the Father, to learn that he's expected to lead thousands of "punishment" worlds, full of history's mortal sinners, to holiness, etc.
Besides added complexity, I can't imagine adding yet another important group to the story and being able to do them justice since there is so much already going on, both visible and behind the scenes.
One alternative way to do it might be to have Satan doing things in the Holy Land that even Connor isn't aware of. Satan already places demons at strategic locations throughout the Holy Land to help Connor further the idea that he is Christ. Some of them could cause unexpected events to occur that result in deaths (mainly guards) even Connor didn't expect. That might trouble him enough to at least begin to question what he's doing by the end of book one even though he doesn't yet know about the gene that enslaves him.
I haven't really thought enough about how best to make things less repetitive in the Holy Land yet. I have a similar problem in Rome in that the investigations led by Campagna and De Rosa in book one are too episodic. They don't really build toward an increasingly interesting/thrilling investigation. With each investigation, Campagna should be getting closer and closer to the truth. Instead, each crucifixion in Rome happens, is investigated, leads to a plan, the plan fails, lather rinse repeat. The clues that build up after each crucifixion may have to be ones that Satan himself leaves behind in order to continue the cat & mouse game while Connor builds toward being Christ.
I have to work out solutions to those issues in both Rome and the Holy Land sometime soon, though. As I have to start writing v2 of the first murder investigation very soon, probably within the next three chapters.