If there is a single currency, then RBI will end up making most of the financial decisions for the block, especially if we include other countries like Nepal, Sri Lanka, Bangladesh and Bhutan.
Which would mean all these countries would become our "bitch."
Even if we consider this happens over the next 10 years, India would be nearly the size of today's US economy by then. So, any financial shocks from these smaller economies will be absorbed by the comparatively massive Indian economy. For eg: A financial problem in Bihar, which is a big but poor state, or in Assam, which is a small state, won't really reflect badly on the entire Indian economy which may comprise of multiple very rich states. Even less if the financial institution of a country like Pakistan fails as a lot of our economy is dependent on domestic consumption. So, if a country like Pakistan fails, we can always bail them out. That's practically buying the country.
Win-win for India and Pakistan in financial terms. No chance of war and most of our current problems with Kashmir will become secondary. This will remove Pakistan as an enemy, they can reduce their defence expenditure to reflect their economy and we will have a lesser chance of seeing a two front war with China. So, Win-lose in favour of India in political terms.
