India is doing it every season if you don't know. In every season whenever flood situtation become bad in Bihar, it opens all the 109 gates of Farakka, and water rush into Bangladesh and causes flood.
No matter how many dams you build, Ganges provides only a certain amount of water. Most important question is why your govt. would build dams if it has no economic utility? Just to teach Bangladesh a lesson? Isn't it ridiculus? Farakka dams was built to provide water to Kolkata port during lean season to maintain it's navigibility by diverting water to Hugli river. It already causing problem in Bihar, flood situation in Bihar get much worse due to adverse effect of Farakka dam. Because dam causes siltation in upper riparian areas. Bihar chief Minister often urge to dismantle Farakka dam.
You can not build dam on brahmaputra river because there is no economic need of it and it will worsen flood situation in Assam which already experience major floods almost every year. Assam does not have enough agricultural land in need of water storage for dry season for irrigation. Daming Brahmaputra does not make any sense for Assam, rather it will be suicidal for them.
West Bengal and Sikkim already dammed Teesta river on dozens of places to produce hydro-electricity and uses for irrigation. They have already utilized that river to it's fullest. For this reason, Bangladesh get negligible water during dry season but experience flood during monsoon season. but we are coping and trying to build Teesta river barrage and dredging to hold water for lean season to use that for irrigation. Also trying to reach an agreement with Indian govt. for fair sharing of its water, but no avail so far. So, I do not know how can India create more pressure on Bangladesh by using rivers when it already doing that to it's fullest?
Aside from Teesta, daming other trans-boundary rivers, most of which are small tributaries and branches of Ganges-Brahmaputra does not have much effect. Neither it will be needed for India, nor it can harm Bangladesh. Who will be the stupid to dam small rivers in plain West Bengal or Assam good for nothing? If West Bengal or Assam needed to dam those trans-boundary rivers to get water for irrigation, then it would have done long ago just it has done to Teesta river. But they did not, which means there is no utility to dam rivers other than Teesta for West Bengal. For the sake of argument, suppose, India built hundreds of dam just to teach Bangladesh a lesson, so what? 90 percent of water flows through river during monsoon, when India can not hold water, it must release water towards Bangladesh unless your govt. want to turn West Bengal, Bihar and Assam into a vast inland sea. Bangladesh can hold water during monsoon and use them in dry season for irrigation by building several barrage projects. So it would be a futile exercise on part of India.
You are arguing just like a child for the sake of arguing without knowing anything about hydrological realities in this region.