Are you kidding ? do you know anything about South Asia ?
India will never reunite with Bangladesh because they hate Bangladeshis. They regret creating BD because in the upheaval of the hype they helped create, over 10 million Bangladeshis took refuge in India and never left. Two of Indian States ( West Bengal and Assam ) are on their way to becoming Muslim majority States thanks to the illegal immigrants from BD.
Unlike Pakistan which has Cultural Affinity with Northern Indian states, BD has common culture with West Bengal only. Rest of India hates them and curse Indira Gandhi for creating BD problem for them.
Pakistan always welcomed Bangladeshis and even today there is a huge Illegal Immigrant Bangladeshi community in Karachi. I was also pro Bangladesh till lately. Recently Bangladesh has been backstabbing Pakistan because of AL Hasina and I am becoming Anti-BD myself. Bangladeshis will have to take care of this Hasina issue or expect very little from Pakistan in terms of support. I foresee Pakistan becoming increasingly Anti-BD in international forums if this Hasina govt. stays in power.