Doghouse Reilly: Yes, I do think India would be concerned by a fundamentalist regime in Pakistan. Very concerned. But I still don’t think they’d attempt to occupy Pakistan to prevent or oust one. Let’s look at some likely scenarios:
#1 - Revolution occurs from the ground up. Pakistan military stays overwhelmingly loyal to Musharraf. In this scenario the rebellion fails ( at least short term ) and India is prevented from intervening by both Pakistan and the United States. Possibly excepting Turkey, Pakistan’s military is the most formidable in the Muslim world. As long as they stay intact, loyal, and supplied ( all big ifs ), no coup will be successful.
#2 - Pakistan’s military remains intact and functional, but goes fundamentalist, ousting Musharaff. In this case the U.S. and India are screwed. Again, Pakistan’s army is nothing too fuck around with. They’re not half-trained levies with crappy morale like 70% of the Iraqi army was during the Gulf War. If they choose to deny the U.S. and India, the cost would be too high to attempt to maintain Musharaff or a related regime. At least for India ( IMO ). It would take a committment of at least two-thirds of the Indian army ( at least 600,00 troops in other words ) to even attempt to breech the border, let alone occupy Pakistan in the teeth of full-on resistance, with little guarantee of complete success ( India did pretty decently in 1971, but they weren’t even close to breaking the front by the time peace was declared ). No intervention occurs.
#3 - Pakistan’s military fractures. Some coherent chunks support Musharraf, others do not. In this scenario Musharaff struggles for control, possibly accepting aid from the U.S., but refusing it from India in order to maintain some semblance of legitimacy. The U.S. seeking to prop up Musharaff concurs - As indeed they must, as a Pakistani faction allying with India would be the political kiss of death. India is prevented from intervening by the U.S. .
#4 - The Pakistani military disintegrates into ineffectual chaos ( as per Iran in 1979 ). This would be the scenario, if any, that would invite full Indian intervention. But India is the archenemy of Pakistan both politically, and after all these decades, to some extent in an ingrained cultural sense as well. Any Indian intervention would trigger wide-scale revulsion and cause Pakistan to rally against the “invader”. The Pakistani military would spontaneously reconstitute ( as occurred in Iran as a result of the Iraqi invasion ), the people would rise and India would be in a mother of an unwinnable guerilla war. Again, I think intervention is highly unlikely.
Now, as I said, I don’t put it past India to try to rearrange the borders a tad during any of the above scenarios. But I think in terms of cost/benfit analysis, the potential threat of a fundamentalist regime which is almost bound to be fragile and prone to implosion ( perhaps with a helping hand from the U.S., or even, clandestinely, India ), is less than the certain cost of going in to the epitome of “enemy territory” and attempting to put in place a government that by its very nature will be illegitimate in the eyes of the people because it is backed by India ( and annexing Pakistan would be out of the question - It would be like Israel trying to annex Syria, not worth the headache ). A fundamentalist regime is a threat to India. But not an apocalyptic one. Pakistan is far more vulnerable to a nuclear exchange and India’s internal security apparatus is impressively large.
And to repeat myself - I still don’t think India gives a shit about Afghanistan, specifically. Even if, somehow, they did end up occupying Pakistan, I can’t see them stretching themselves even thinner to hunt guerillas in the Hindu Kush. For cultural reasons I regard Taliban-style fundamentalism to be unexportable en masse to India’s Muslim population. Hell, it hasn’t even taken hold in most of Afghanistan ( many folks there may be fundamentalists, but they mostly aren’t on the Taliban’s wavelength - The difference is sometimes referred to as “ultra-fundamentalist” vs. “fundamentalist” ). Before this mess happened I was predicting an eventual implosion by the Taliban in the near-future - Opposition even among their “allies” was on the rise. The al-Quaeda are a threat as a terrorist organization, but India is not their primary concern, and crushing them in Afghanistan doesn’t remove them as a threat anyway.
A final point - India does want to be viewed as a great power, I’m pretty sure. But they were a founder and the prime mover behind the Non-Aligned Nations and seem to take that status very seriously. Not quite to the Switzerland level, perhaps. But I am of the opinion that they wouldn’t have any interest in any strategic alliance with the U.S., even if offered. It would run contrary to their current political culture. It might even create internal difficulties that could unseat a government.
Nope. I still don’t think your scenario is likely. Just my $.02 
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