If that's your worst case scenario, I'd consider upping the thread level to bloody-hellish case scenario.
Supposing that the Pakistani Army somehow crumbles, the Talibunnies take ove the government, where do you think they'll go next? Kashmir. If you think Kashmir is bad today, wait till the Taliban team up with Al Qaida to cause some real mayhem.
Today, at least you have a state to deal with which is to some extent answerable to the UN and to other global powers. The Taliban has no such qualms. They'll be so emboldened by their victory in Pakistan that they'll pull out all the stops. The entire Af-Pak region will turn into a breeding ground for Jihadists (yes, far worse than today).
With the Pakistani Army, atleast we know that we can defeat them if they try and attack. But these mujahideen aren't the kind who sign surrender documents and then keep quiet if you get the drift.
I think the horrors of such a situation are too scary to contemplate. Lets be good and try to beat our neighbour into a functioning democracy. That's the only way out IMO.
Well, lets rewind a bit...exactly a year before, India was attacked with impunity by Pakistan in Mumbai killing 200 odd Indian and foreign citizens. India fumed with anger, MEA(and a part-time PM then) Pranab Mukherjee announced 'all options are open'. Then Pakistan upped the ante, they threatened a nuclear war if even limited strikes were attempted even in POK. What happened? India crumbled under the nuclear threat. Then India tried to use diplomacy, because our leaders like you believed that Pakistan is still to some extent answerable to UN and other powers of the world. What happened? Absolutely no progress in the case of Hafiz Sayeed. ISI/PA go scot free after attacking India. Before that India was attacked in Afghanistan. Again after one year India's consulate again attacked. What has India been able to do?
Two reasons:
1) Of course, we can defeat the PA(because they are only good at creating and arming terrorists), but we wont get a chance to do so because PA will use the nuclear card and continue to wage war against India while India watches helplessly.
2)Pakistan gets funded by the same powers that are expected to curb its terristic ways. These funds are then used by Pakistan for anti-indian activities(recently admitted by Gen.Mush in as many words).
In the present condition that Pakistan exists, India can be engaged by Pakistan perpetually without any fear of impact.
But, if Taliban defeat PA and takeover Pakistan. Then, the first thing that will come into focus would be Nuclear arms of Pakistan. Nuclear arms of Pakistan today are only meant for India and everyone knows this. But if Taliban takeover, then they will extend the nuke blackmail to everyone else i.e US, EU, China, Israel, India. We will have company and they will be forced to act.
If you imagine Pakistan as a snake and its nukes as venom, then right now the snake has been trained to strike only us. But if the snake turns 'rogue' and can potentially attack 'everyone else', then 'everyone else' will take steps to defang(denuke) the snake(pakistan).
Then in the present scenario the Pakistan will keep getting aids from the powers that be inspite of knowing very well that these funds will be used against India. But if Taliban, takeover then such an arrangement is not possible and evenn the mighty taliban cannot fight without funds.
Now, consider a situation where Pakistan somehow survives the present crisis in its present form. If and when, US retreat from Afghanistan, Pakistan will put back the old arrangement. That is, talibuddies go back to torturing Afghanis and provide footsoldiers for Jihad in India, while PA lords over both Pakistan and Afghanistan. In this scenario, India(particularly Kashmir) would face the terrorism to the levels of 1980 again. Therefore the doomsday scenario that you fear can still come true, even in the present situation.
But if Taliban do takeover Pakistan, then the powers that be would be forced to act on Pakistan. Pakistan would lose all remaining credibility to stake claim on Kashmir. Taliban are international villians and everyone will find it legitimate if they are crushed. PA is only villian for India, when it stakes claim to Kashmir, then it seen as legitimate by international audience.
Lastly, taliban/pushtun fighters in Kashmir is not new. IA has dealt with them in the past and we can do so pretty well in the future. Our COIN ops capability need not be underestimated.
Lastly, Taliban are really successful in Pakistan because they enjoy sympathy from all quarters. There is a maddrass in every corner of Pakistan that brainwashes people. So, Taliban's success in Pakistan does not guarantee its success or even threat in India.
Therefore, Taliban gaining ascendency in Pakistan is in no way detrimental to the interests of India. Infact, that could pave way for future nation-states of Sindh, Balochistan and Pakjab that can then be forced to dance to the tunes of India.