I agree, your scenerio is plausible. But why would the FBI fabricate a "suspect" at this point? It seems to me they could just stick with the "we haven't a clue" theory of the past nine months.
In a few days you'll see this in long-shot. Then you'll see that they didn't so much fabricate a suspect as shoot down a theory. Very publicly. This is shifting the scenery for what is going to happen next.
That's the fly in my argument's ointment, agreed. My only thought is that they may have initially suspected him (and maybe others) but later found evidence pointing elsewhere and just are stringing the old suspicion along as a helpful distraction. Or, perhaps the investigators don't know the whole story either and are being allowed to wander down a garden path. Admittedly a horrible way to treat a citizen but there are huge things (lives) at stake and the gov may not be willing to risk the agents in the field being a little leaky. As someone suggested vis a vis detaining illegals in the U.S. "we can always pay reparations later, best to be safe for now."
Still, I can't help but think there's something very big in play behind the scenes that will shock many people when it comes out.