There are three questions here.
The first is the military practicability. I'm not prepared to offer a final opinion on that, but consider how the United States failed to occupy either Iraq or Afghanistan effectively.
The second is the legality on an invasion. The justification might be construed under something like the Responsibility to Protect. However, R2P envisions an international consensus and an international response. There are precedents for a consensus without the UNSC (i.e. without some of the veto powers of the UNSC), e.g. some of the events around Syria. Still, just one country going it alone would be pushing things.
The third is the legality of an annexation. When one goes in under R2P, that is ostensibly to protect the local population, not to grab a piece of territory. The response to a blatant land grab could be sanctions by some (but not all) of the international community, as in the Crimea exampe.
On balance, the answer is a qualified no. India would pay a massive political and economic price. Nationalists might decide to pay it.
