(Race concerns? I gotta hear this one ...)
One of the options was turning the Montauk line into a subway to serve Maspeth, Ridgewood, Middle Village, Glendale -- the last homeland of working-class white New York -- into Jamaicia, then down to Southeast Queens -- the largest concentration of middle income Blacks in the city. Well, the neighborhoods FOUGHT to STOP the subway. People were amazed. The city was used to people fighting to get service, but not fighting to avoid it. People were afraid Blacks would ride the subway to their neighborhood, commit crimes, then ride the subway home. Back then, no one imagined that Black people, or criminals, would drive.
Among other things, the battle launched the political career of -- get this -- Geraldine Ferraro. She marched from one end of the line to the other, announcing the line would be built over her dead body, and was elected to a seat in congress that included both this area and Astoria. I've been told this story many time by the old timers at City Planning. Some liberal, eh?
In any event, the NIMBY/bigots needed have gotten all excited. If race concerns hadn't killed the line, NIMBY concerns would have.
Another option was a Queens "super express" branching off the QB line and running to two tracks of the LIRR before reaching the tunnel. The turn out could have been used for that, too.