Everyone in this thread keeps saying we should do this that and that. Modi and his admin won't. No point in discussing. The costs outweigh the benefits. We could invade Bangladesh, wipe out the BNP/Islamists and create a safe zone for Bengali Hindus (or allow them to migrate to India), but we'd be stuck in a gurella war for decades, weakening our economy and military - exactly what China, and to some extent US wants. Not to mention international pressititutes would accuse India of basically doing another Russia/Ukraine situation (they're hyping up Khan Younis as this angel figure, and downplaying Islamist violence) and we'd be hit with sanctions and all sorts of bullshit. An airspace and naval blockade wouldn't be as costly, but the international reaction would be the same.
What we need to do is secure the eastern Radcliffe line and drive out the illegal Beggardesis, and figure out a way to get Awami League back in power. Citizenship Amendment Act was already criticized, but they at least didn't do sanctions. Unfortunately the latter won't happen, Islamists have taken over and will allow US/Chinese bases, so external forces will keep them there as much as possible. Awami league was also incredibly unpopular domestically against because of radicalization.
Creating some kind of anti BNP Islamist faction to fight a civil war and keep the country unstable so that it becomes more of a headache than a benefit to US/China could be possible - like arming Bangladeshi Hindus and creating a Mukthi Bahini 2.0, but then US is going to retaliate with funding Khalistan and denying visas and all sorts of shit.
It's a horrible situation with no easy solution.