Let us analyse this without emotions.
What is the strategic value of Bangladesh?
Strategic value would tantamount a flow because of a country’s location, or its economic worth to make a dent in the world economics, or its military might which can be a gamechanger or its political clout and leadership on the world stage (as was that of NAM when the colonial infrastructure was being dismantled around the world.
I leave it for discussion as to which of the criteria Bangladesh fulfils.
To believe that the NE of India is insecure because of Bangladesh would be an exaggerated and opiniated thought. The cartography has not changed over history since Independence. The adversaries remained the same till 1971. If it did not matter then, why it should matter now, more so, when in 1971 the Pakistan Army could not do anything about it and the Pakistan Army was no pushover.
The issue of China being able to anything worthwhile against India in the NE is another pipedream, if one understood the manner in which wars are fought and also the terrain. Without getting into the operational aspects, which would not be correct, suffice it t say that had it been possible would China have withdrawn from what was known as NEFA in 1962, when they did not do so in Aksai Chin? The reason is that it was not feasible since artillery could not be brought up to support operations as it was a mountainous terrain with no existence of roads to permit artillery to be brought up. In Aksai Chin it was possible because it was a Plateau.
Also, take the issue of Kashmir. If it were such a cakewalk, then is it not surprising that even after four wars there is hardly much of a change in the territory from what was after the first Kashmir War? Surely, both India and Pakistan are serious about their claims over Kashmir.
What looks simple on paper or during drawing room chats, is not the reality on the ground.
India’s eastern flank was secure in 1971 and it is secure even now. A look at the map and the force level indicate so since Bangladesh is surrounded by India including the Bay.