as you said atleast with India & China you can trust the leadership, the nuclear commands of both countries will be presumably efficient and according to book of rules.
the real problem could be with Pakistan as they have two leaderships. Army and the democracy. who commands nukes at that certain point of time is a mystery to everyone. It could be exactly just like the one shown in movie. but it there it was Captain Vs XO and here it will be Army Vs leaders at political level.
In a scenario of conventional war, we just do not know who commands the nukes if the Army takes over the command right in the middle of a war, what will everyone in the chain of command do? right to up the person who has to press the button.
even without Army revolt, they still control nukes like during Kargil 1999. But still our leaders would be communicating with their democractic leaders and would not have any communication with Army generals. Its very important for person who is in highest command of nukes to continuously communicate with his counterpart during conventional war scenario. unless we discuss our intentions about launch of nuclear missiles, things could lead a bigger confusion and lead to unnecessary misunderstandings.