It's easy for us to Invade GB region. Reasons.
1> Population of GB is very less. Only 0.5 Million in big region equivalent to Punjab.
2> Pakistan supply comes from NW region. We can open
three more fronts from Tajikistan Airbase / A'than Army + P.O.K (next to Jammu region) + Siachen.
3> 70% of Pakistan army HQ at Islamabad till Karachi. 20% in near A'than border and only 10% in GB region. Due to difficult terrain and high mountains, It will take long time for troops to mobilise. Not to forget we can use 3 more fronts to stop/block them.
4> We can open Rajasthan-Gujarat front from 30 such conflicting point by sending 2 Strike Corps + 2 Hold Corps. Also Block Pakistan Punjab Army poisition by dividing into P.O.K. and Pak Punjab. We can use Ambala Strike corps for that.
5> Block Pakistan Shipment in Arabian sea by using 3 ports @ Oman, Chabbar Port and Porabandar.
6> Surprise and Offensive strike against Pak military instalment. All are in 200 Km range.
7> By giving few Bn $ military aid to A'than for start conflicting Durand line. Also Baluchistan.
I don't think Pakistan will use Nuke, But let say they use. We can buy S-400 and develop & deply AAD-PDV by 2015 in big numbers and Buy 100 more fighter jets and deploy @ Bhuj till Halawara.
I may be sounding as Day-Dreamer, But Think Logically, It's dificult but very much possible if we plan well and implement all in next 5 years !!