I have a pretty interesting idea; an alternate subway thread. It is a what if scenario where forgotten proposals and subway lines (as well as the SAS, and IND Second System) actually became a reality, minus the events in the world that didn't take place.
Rules
Make sure it is a real proposal, not a fake one, or one that you made up.
Limited foaming
Also make sure you adjust the subway services too. This also includes how the alternate event would affect NYC today.
I'll start mine.
The Great Depression and WWII didn't happen, so the IND Second System gets the green light to build up all of its planned extensions, expecting full completion by the late 1940's. It is the biggest subway project ever in New York City's history
Now, post how service would be if the IND Second System would be serving NYC in the present day.