1. Dealing with BD military will not be a 3rd front, but 0.25 front where even BSF can manage them. Our CAPFs has more experience than them. 3rd front means requirement of deployment of critical military assets. BD air defence will be obliterated in the first 3 hours of engagement. Their artilleries and navy will go next. Op problem will ensue once the large targets are gone and Indian army moves in where they will face resistance in ground in form of guerrilla warfare, which as history is witness, becomes most costly - by blood and resources.
2. India will never dare to arm them because that will give justification of the Kukis, Nagas etc. in international fora.
3. BD Hindus' best bet it now cluster in and arm themselves with tools. The BD army won't allow guns to go against Hindus, because Guns are restricted in BD and can turn on the army themselves at later date. So, hindus must cluster and fight till some sort of normalcy returns in coming weeks.
4. What India can and should do is issue message through diplomatic channels that if the chaos spills over to India or not brought under control, the BD will find a irate and angry neighbour who will teach them a bloody lesson in years to come. BD will need the borders of India to open for its economical survival. The agitation that grew on the backs of inflation, can bring doom to the new regime too if Indian border stays closed.
But, the actions of GoI in trying to block x handles disseminating atrocities on Hindus says to me that the Modi govt wants the trouble to just go away on its own. Disappointing.