C14 W is of course part of a MARS gate, and they are not supported by the simulator, because you just can't place overlapping position without causing issues with AI and AI ground services. Since we are planning to update GSX in the future to have its own support for MARS gates, that would work bypassing the standard system, it wasn't really worth adding that gate, and cause issues with AI, unless you renounced to C14.
Considering the lack of heavy airplanes in MSFS right now, it was best giving priority to the non-heavy gate.