What happened back then was truly sad and I believe Quid-e-Azam should have awarded East Pakistan full provincial autonomy right from the beginning. It would have been good for both sides, and saved countless lives. I don't think India was the ultimate winner (neither of three were) for the former East Pakistan emerged as an independent Muslim majority country and a member of the United Nation. India would have won had former East Pakistan annexed with India in any form, which did not happen.
I do believe the federation would have sustained itself had civilian leadership of PAK was more pragmatic and the army didn't intervene from the start. Even in 71 if mujib was allowed to be PM he most likely would not have lasted the full term. Worse case scenario- it would have been an amicable separation with strong bilateral ties. He wanted to be the PM of PAK as he was a typical politician with ambitions but 0 administrative skills. Bhutto was worse though. He was the primary reason for 71 debacle IMHO. His racist feudal mentality came very handy to Indira gandhi.
I guess it was a partial victory for India. Did u know many WB intellectuals were dreaming of annexing BD/E.PAK and i don't think it was completely out of Indira's long term goals. But E.Bengal political dynamic didn't allow their wet dream to materialize. If BD becomes strong with AL and other indian dalals firmly in the pages of history with no trace in BD, then u can say that India lost in 71.