Yeah, I've picked up on that in a couple of places since I drafted this post, though I have yet to see a reference for it. It wouldn't really change my theory much. Admiral Marcus could be the head of Section 31, or Section 31 might not figure into it at all, just some branch of Starfleet with nefarious motives.
Then again, if Gary Seven had been alive and manipulating events on Earth and throughout the Federation for 250 years, he certainly wouldn't have gone by the name Gary Seven that whole time. Maybe Seven is
Admiral Marcus and Carol Marcus is his daughter. Total speculation, sure, but so is everything else.
Personally, I think Gary Seven as the founder and head of Section 31 makes perfect sense. Wouldn't be the first time Hollywood has taken a protagonist and turned them into an antagonist as time and tragedy or other forces have worn them down.
Also, I can't get over how much Peter Weller looks like Robert Lansing.