Here is my Common Sense take on the issue.
The single best argument against Oswald being part of a conspiracy is that he got his job at the TSBD well before anyone knew a presidential motorcade would be going right past that building in late November. Whether one postulates Oswald was a shooter as part of a conspiracy or patsy chosen to take the fall, the plotters couldn't have known that the job at the TSBD would give Oswald a the perfect perch to shoot JFK from. Even if they knew JFK was coming to Dallas, they would have to have specific knowledge that there would be a motorcade and that it would pass directly in front of the TSBD.
The CTs might counter that the conspirators just took advantage of the situation when they discovered their shooter/patsy was at a workplace overlooking the parade route. The question then becomes, why would they have selected Oswald for either role if they didn't know in advance of the golden opportunity his employment at the TSBD would present. Why would these conspirators select an average USMC marksman to do the biggest contract killing in American history? It makes no sense. It is also a bit far-fetched to think they had already contracted with Oswald to do the shooting and just got lucky when the motorcade route was announced. What are the odds of that happening.
Then the CTs might ask, didn't Oswald just get lucky when he learned of the motorcade route. Yes he did, and if Oswald was the only mentally unbalanced person in the country with a rifle and a propensity to commit such a heinous act, it would have been a remarkably bad piece of luck. But the fact is there might have been dozens of such people in the country, maybe hundreds, who would have done what Oswald did if given the opportunity. Given the fact we had a President who traveled all over the country and had a fondness for riding in slow moving motorcades in an open top car, it's not at all surprising that he eventually might cross paths with one of them. The key word here is "opportunity". This was a crime of opportunity. Oswald won the assassin's lottery when JFK's motorcade was routed right past his workplace and he took full advantage. Maybe if another site for the luncheon had been selected we would have never heard of Lee Harvey Oswald. Maybe it would have been another assassin in another city at another time who was dealt such an opportunity or maybe it would never have happened at all. Life can be that random. Who could have guessed that the choice for the site of the luncheon would have such devastating consequences, but that is what happened.