Guys you have to understand couple of factors...
1- In most of the discussions involving a threat to Pakistan, many posters says that Pakistan is a nuclear armed state so it is too big to fail...You are right..But this is your approach which is making Pakistan hollow inside...
2- ISIS and other jihadi Islamic organization will not came face to face like a regular army kind of thing to fight with you..They are border-less organization and they will fight within Pakistan itself in the form on terrorism,..So the usage of nuclear power is just useless option...You are not going to use nuclear thing to terrorist.
3- The challenge to ISIS is not that some one from outside will come to fight rather ISIS is a concept and ideology replacing Al queda in 2000-2013...And Pakistan should fear to the ideology and its impact on the mushrooming Madrassa educated youngster rather than thinking some one will come outside...Once the ideology and concept is popular and where Pakistan is very much a fertile ground to be like that, they no army in this world can fight with them...You do not fight concepts and ideology with powerful army....You have to fight with them with strong civilian and religious leader who can differentiate and guide the public about the righteous path.
4- Pakistan created a monster in the Afghanistan and Pakistan border by not integrating your tribal areas to mainstream...That is mistake that you have done...You can not create a state withing a state where some tribal people can do all the terrorism across the world and inside Pakistan too and go unpunished..
Hence wake up dear...fight with Islamic radicalism with all of its forms,,,Otherwise, with the quest to defeat India, those terrorist groups which are patronized by Pakistan , will be front and out soursed organization for ISIS kind of outfit in future which will be tough to control if not controlled now.