Come to think of it, the Hindus in Bengal would probably rally around the Communist Party, because if they want to secure Hindu interests, it would have to find sympathetic Muslims as well, seeing as how Hindus would be in the minority, and the Communist Party would be one of the few secular forces out there which can unite both Hindus and Muslims (Muslim dominance in the gentry and in the overall population ensures that Muslims end up controlling the military as well, and so the military would want to protect Muslim interests, so any possibility of a secular nationalist military dictatorship like in Turkey or Egypt would be pretty difficult unless you get one idealistic general who does believe in secular Bengali nationalism to somehow take total control of the country, like how IOTL the Pakistani military in the 1970s was fairly secular, yet all it took was one Islamist general, Zia ul Haq, to change the total structure of the Pakistani military and Pakistan altogether. I don't know who that general would be, considering the fact the Bangladesh's OTL military dictators, Ziaur Rahman and Hussain Ershad, have all been friendly towards political Islam in one way or another, with the former adding ""Bismillahir-Rahmaanir-Rahim" to the preamble of the Bangladeshi constitution and the latter declaring Islam to be the state religion of Bangladesh).
Religious violence only happened in the Indian and Pakistani independence because the countries were based off of religion (well, Pakistan was anyway) and as such the Hindus and Muslims who found themselves living on the wrong side on the border had to move, and throughout the process there was plenty of violence. With unified Bengal there is no incentive for Hindus and Muslims to move, the Bengal province would just change in political structure, lower the British flag and raise the Bengali flag (btw, how would a flag for unified Bengal look like? The OTL Bangladesh flag was made by separatists in the East Pakistan era, and since that doesn't happen ITTL the Bengal flag will probably look different).
I can also see India aiming to break off the Hindu parts
India was never really a country looking to unify all of the Hindus. If it did, it would've annexed Nepal, and laid claim to the Hindu Tamil parts of Sri Lanka, the Sindhi Hindu parts of Pakistan, and the Bangladeshi Hindu areas. If the Muslims end up getting too arrogant with their position in Bengal and begin abusing the Hindu population, then I imagine that there would be a Hindu separatist movement (
there was one IOTL), but of course that's a pretty big "if" because the Hindus, too, have a sizable share of political power, so I can imagine that the most Muslims will do is try to secure the privileges they already have and not to do anything which might improve the position of Hindus, rather than actively trying to oppress and hurt Hindus.