Censin,
Don't you think it would be confusing if passengers see the again? They'll think it's going to Forest Hills, unless you do this:
Have the run to 96th Street at all times except late nights when it will short turn at Myrtle Avenue. On weekdays it will run via 6th Avenue local, on weekends it run via 6th Avenue express.
Have the run rush hours only to Forest Hills from Second Avenue temp to reduce the confusion between 96th Street bound trains and Forest Hills bound trains.
NOTE: The would operate internally as part of the , NOT as part of the .