One official language for a country keeps the country united. Even India tries to promote Hindi everywhere. Tibetans in China learns Mandarin. Pakistanis be it Panjabi, Sindhi or something else have to learn Urdu. Assimilation is the key.No, it is not. Even the mere thought of doing so would be a sin. You can still be together without impinging on each other rights.
You must be aware of the Bengali language movement in Assam's Barak valley in the early 60s when the state totally disregarded the bulk of Bengali population's concerns by declaring Assamese as the sole official language. People sacrificed their lives in protests and 19th may is commemorated as Bhasha Divas. Assamese government eventually backtracked.
You cannot expect people to forego their traditions in order to assimilate into the greater society without any repercussions.
There were many persian/urdu speakers in Bangladesh. Eventually they mixed with the Bengali speaking people. All for the sake of national unity so that no one can break us.