True, but then the parking line at Ghatkopar will need to be converted into an island platform. That will be too narrow for the long distance trains, and providing escalators/lifts on it will be very difficult.
Furthermore, long distance passengers usually have a lot of luggage, which may not suit metro travel. It will also be difficult to carry the luggage on long and crowded concourses down to platform and walk on the narrow platform towards their coaches.
TNA may get halts for more trains once the KYN side ramp FOB is fully...
more... repaired and becomes operational. Anyways, TNA needs another FOB towards LTT end to connect PF 1 to 5-6 and 7-8 with exit to eastern side and lift/escalators for PF 7-8. That will make halts for more trains easily manageable at this most crowded station in the Mumbai area.