similar experiment already done with 12015/16 NDLS-Ajmer Shatabdi where locomotive used in both directions . In result the time was reduced nearly 20 mins in 440 km journey. As the time reduced was not good, so railway drop this idea.
As the distance between stations are less and between them also so many TSR and PSR , so fast acceleration and retardation are not good because there will be too much jerking.