Personally, I would give India a seat, the dispute, though annoying, is hardly relevant. What is relevant is China's on going face off against the United States. What we need is a country, just like India. Not so close to us that the West would find objectionable, yet very close to Russia that would mean stirring the pot more than it is now and take some heat off China. The Ukraine crisis proved India's stance.
The UN at this point is just a stamp of approval China uses as legitimacy for certain peace keeping missions, and international operations. The UN will no more block China's way as a deer could of a truck. China's progress in the China Seas, Africa and more speaks volume.
Last, this particular move, won't make India an ally, but it will keep India neutral on a lot of he issues, and neutrality from a permanent member is very important. As we have seen the UN takes a very if you are not with us, you are against us mentality, thus, what seems like neutrality, would be in fact taken as a seal of approval.
To sum up, India is perfect to muddle the pond, and give the US something else to deal with, while we proceed to finish our own mission.