India won't be a good choice as it would furstrate its neigbors. India already lots of issues with its neighboring countries. I would say keep it as it is. The US, Russia, China and Britain are good enough.
There are boundary problems between China and India, but they trust Putin so they are able to work together. The main problem would be Pakistan, so you are right. I don't know how they would be able to put a new member in the security council without others going ballistic.