(1) Gatiman's speciality is it being a super premium train(much better than Shatabdi). Its fares are higher than Shatabdi due to much superior on board facilities/food and train host/hostess. AC DD is a higher volume and inferior travel than normal ACC and its fares should have been kept a bit lower than ACC. So ACDD coaches in Gatiman shall go against its super luxury status. (I wonder what would be difference between the Gatiman & proposed Tejas & Shatabdi of course)
(2) Mumbai-Pune is excellent destination for ACDD but existing rail route is longer than Mum-Pune express way route, it is full of curves and steep gradients since it was planned and constructed about 150 years ago. A cumulative effect is much...
more... higher journey time than buses/ cars. So major traffic is on the Mum-Pune expressway
Today a straight rail track without curves and gradients but with longer tunnel route & without any speed restrictions/ banking loco is possible. Such track shall have higher initial cost but the recurring saving of fuel cost, journey time, operation/maintenance cost shall make it a better option.
I personally wish that instead of extra track from Kalyan-Pune, IR should construct straighter route from LTT to Pune via thane creek which may be any where around 120-140km long. This may run parallel to existing tracks for some length (LTT-Vashi, and for some distance from Pune along Pune-Karjat line) and run 160kmph+ full ac trains (60-90 minute journey for non stop/with stops journey) and 130kmph non ac LHB trains (75-105 minute journey) in large numbers. Passenger response to these "desi bullet trains" shall give a good indication whether bullet trains for about 500km journey shall be be successful in India or not?