There is one conspiracy theory I have that probably LN might accept and that is that someone figured out Oswald was a Bipolar personality, and possibly OCD, after the Walker shooting, so they figured if they could put Oswald in proximity to a target that he would feel compelled to shoot at, because of his mental illness, then he probably would do so.
So they set up a job for him, in the TSBD, or they found out he had a job in TSBD and because of their connection to LBJ, were able to suggest the route for the JFK motorcade should pass by TSBD. Then all this conspirator has to do is sit back, make sure his building has no security and allow his Oswald employee have access to all floors. Then its just a matter of probability, and the conspirator(s) may have actually calculated the probability was "high" that the Oswald nut would take a shot at the POTUS motorcade.
That conspirator could have been the owner of TSBD, David Harold Byrd, who certainly was in the camp of rightwing element that disliked JFK and probably considered JFK was a traitor. After the tragic event, Byrd, removed the window frame he thought was the sniper window and hung it in his gallery of dead animal heads.