1.
India should work with pakistan and Bangladesh to make the subcontinent stronger. Bangladesh being the youngest of the three should be given every incentive in the book for development for economic progress and education by India.
India should provide diplomatic and economic support to Pakistan in return for ceasing of all terror activities against India. Kashmir valley should be jointly governed by Indo-Pak by the approval of kashmiri people from both sides.
2.
If pakistan or bangladesh tries to take advantage of their geographical locations to create insurgencies in India, India should engage in overt and covert operations against both. Garner heavy diplomatic pressure and economically strangle and hurt the economy of countries in it's immediate strategic neighborhood.
3.
Strategic Allaince between Ban and Pak.
If a strategic allaince is forged between Bangladesh and Pakistan, it poses no problems to India. If bangladesh wants to aggressive posturing against India, it will be their loss. In any case of ban-Pak allaince cannot achieve the strength to militarily shy India on the eastern front. So if bangladesh wants to confront India, the most effective weapon is ISI, which roughly translates into same pseudo radical islam based breeding of extremism against India. If bangladesh does wants to go into such alliance with pak, they can see the results of the same in pakistan today. Imho ban-pak strategic allaince will be devastating for bangladesh if aimed towards India.
Rather than countering India, just stay non aligned and neutral and benefit from large economies of both India and China. Get Chinese technology in manufacturing and Indian expertise in education and IT, and benefit from it. It will be 1000 times more beneficial than getting missiles from pakistan.