First of all, India doesn't possess thermonuclear weapons, they are interested in it, and so is Pakistan. If India develops it, following policy of minimum deterrence Pakistan would follow suit. You people nuclearized this region in the first place, you started it, we didn't.
Secondly, 120 nukes of Pakistan are more than enough to wipe India off the map atleast 10 times over, no anti ballistic missile system will have a reasonable reaction time in the context of subcontinent, since both neighbours are located at a stone throwing distance, before your system is ready, Pakistan's missiles would have already hit their targets. Shaheen III covers 2750km, brings entire India along with Andaman and Nicobar islands into our hitting range, plus an assortment of other ballistic missiles , Pakistan possesses Babur cruise missiles which possess thrice the range of your Brahmos, along with that Pakistan Airforce possess Air Launched Cruise Missiles Ra'ad which would also be used to deliver Nukes if need arises. Pakistan wants peace in this region, the radical former RSS lunatic, sitting at the helm of affairs in your country , is more than welcome to try to coerce Pakistan, but the reaction would be swift, massive and unbearable for you guys, it will by all means never be a limited war, which your politicians and planners (in the state of a Modi Orgasm) are anticipating !!!
I DON't know from where did you get this but let me tell you some things and will try to eradicate your day dreaming.
Firat of all
India has already acknowledged that India will have its first thermonuclear missiles from mid 2015 from a site situated in southern state in Mysore.
And even Russian side has acknowledged that yesterday there was a article quoting russian officials sating that Indian side is just on the brisk of making H bomb.
Now coming to pakistan -
Do you even know how much research is needed in thermonuclear bombs?
How many years of research is required?
So keep dreaming for your H bomb.
Now coming to your reaction time in nuclear war-
India has GSAT series satellites which are used for BMD. These satellites do reconnaissance, real time search, high sensitive activities and for intelligence.
GSAT series keep real time eye on are around 6000km range for high sensitive activities means it will alert is even if you are moving your BM from one place to another so in a war we will get be getting these information if you are trying to to even transport or move your BM in war scenario let alone the signature of your BM so our BMD will be ready even before you have launched BM so that negates your reaction time issue.
Just having missiles with higher ranges does not mean you have won the war it should hit the target so that it is useful but because oF BMD I can't see they can hit their target.
Genious if you are not updated then let me tell you India possess two types of Cruise missiles one is supersonic Cruise missile Bramhos( which you mentioned) and other one is NIRBHAY( which you missed) which has more range than your Cruise Missile by more than 300 kilometers. So be updated.
In order to deliver nukes on Indian cities you need to pass the border. Any aircrafts just can't appear on the other side of the border like that and start bombing indian cities.
In a nuclear war Indian borders will be guarded by MKI so good luck in engaging them which will be equipped with nuclear tipped missiles and bramhos and after taking care of your front line fighters which are very leas in numbers then Indian mirage which are specially for nuclear programmed will take over to deliver its duty along with MKI so good luck on taking nuclear attacks by two fighters on your land.
What you are missing that when the first nuked missile will be fired from Pakistan to get destroyed by our BMD, you will be given response from 3 dimensional nuclear attack which you don't have and after getting response from 3 dimensional for even one minute will make sure that Pakistan is not on work map.
You are missing the capability of Indias land based nuclear weapons.
India's Agni series BMs are worlds finest and also we will be possessing MIRVS in 2016- 17 which will make our AGNI series even more potent.
Just imagine a Agni series BM with 4 MIRVs is launched on Pakistan and one nuclear load is dislodged on Karachi, other one Lahore, third one on Islamabad and other one on Islamabad.
Imagine what one Agni series missile with MIRV capabilty can do to your pakistan.
Let alone nuclear strikes from other resources.
So think twice before going nuke.