It has been years since I've done a proposal on this thread.
A train service to Coney Island. Every summer, select trains would go to Coney Island making all stops with the . The purpose is that it serves residents throughout the Crosstown line for a one seat ride to the beaches and amusements when the Island is at it's peak, and alleviate overcrowding on the .
Another suggestion is to draw out plans of where the 2nd Avenue Subway should go in Brooklyn should the ever consider extending the line in the future. I imagine a 4-track 5th Avenue Subway with a connection to the train around 36th Street and ending at Bay Ridge where the is. Maybe even an elevated line on the Staten Island Expressway with a tunnel under the Verrazano-Narrows and heading underground afterwards ending at the Mall.