Why didn't the MTA, during the six years prior to the L Line shut down scheduled to start in April 2019, take a serious look at other possible improvements west of 8th Avenue?
You could construct a pocket track one block to 9th Avenue. This could provide storage for trains going out of service due to mechanical problems. It would also improve service reliability.
Dig several more blocks and add a new station near West Street and 11th Avenue. Imagine the benefits of additional service to the growing West Village and Chelsea neighborhoods.
Better yet, turn north on 11th Avenue and build an extension connecting with the Javits Center and 7 train at Hudson Yards.
The most cost-effective time to do any of this additional work would be when the stations are shut down during tunnel reconstruction. The contractor is already on site, mobilized with a staging area for workers, supplies and debris removal.
Going back years or decades later to attempt any of this work west of 8th Avenue along 14th Street will be far more expensive and take many more years to complete.