Suppose that L to 7 Hudson Yards Extension actually happens. (L to 7 Extension) The platforms are offset so the L Train could eventually extend east to Penn Station and directly connect to Grand Central Terminal.
From there, there’s a very convenient connection with the 2nd Avenue Subway and First Avenue - UN Plaza. Add in a new Herald Square L Train Station, and 3 of the busiest transit hubs become connected. There isn’t a 34th Street tunneling conflict since Penn RR lines are under 32nd & 33rd Streets.
Maybe this becomes a reversed “C” shaped SAS revised route. It would include a Harlem Crosstown extension connecting west to the 1 Train. This would greatly improve horrible bus traffic on 125th Street and provide connections with all existing subway lines across Harlem. A third, middle track on this stretch may be a good idea to consider. This area could become, with truly careful planning, the new Uptown. And maybe the trash will no longer be such a problem.
And maybe this Crosstown L just heads north up 2nd Avenue and west across Harlem and we’re done! All those subway lines, Midtown and Uptown, will be connected.
Let’s capitalize on the lines we have in place and get more New Yorkers moving sooner.