Missile Defense for India?

The United States has entered into initial talks with India regarding the possibility of selling missile defense technology to serve as a hedge against the nuclear threat from Pakistan or other rogue actors. According to the Financial Times, technical level talks have been occurring for over two years. India remains undecided on whether they want to purchase the system from the United States. While there is interest from sections of the defense arena in India, the former head of a military think-tank, Satish Nambiar, was quoted as saying the deal, "would have very serious political repercussions here." How would a missile defense system for India alter deterrence calculations in South Asia? Should India go ahead with purchase of the system?