Not very necessary. The route is being electrified and in a couple of years trains will be running thorough from CST to MAS with e-locos. With DD and GTL already having e-loco sheds under construction, and with the sheer number of diesel loco sheds serving this region (UBL, MLY, KZJ, PUNE, GTL, GY), which are slowly getting lesser and lesser work due to electrification in the area, a new diesel loco shed too would not be of much use.
A trip shed will be a good choice as trains can undergo LC here for a couple of years.