It simply isn't possible to stand against social processes. The Awami League had support, it did not parachute into power. It gave way to two dictatorships, one of which was thinly disguised as a political party in power. That alternative political party also enjoyed the support of people. So both the marquee parties had support.
At the moment, the support for the Awami League is rock-bottom minimum, and there are no signs of recovery. That itself is bad for your constitution-making process, because whether the new constitution that you have proposed is drawn up by a constituent assembly (an elected body), or by the interim government, through consultations, or by a constitutional convention, that I take to mean a gathering of political parties by invitation from the interim government and without election, there will be bias, bias inviting a future autocracy.
Where will any country find a universal formula that defies the ravages of time, the changes in the neighbourhood, the developments in the country's economy and ecology and society?
As a citizen of a neighbouring state, this will be interesting, morbidly interesting, to watch.