Old flat demolished by builder,not building new -Not responding

I was the owner of a flat which was old.A builder came into agreement saying he will demolish and give us a new flat which will be of higher square feet area also with better facility(Max 2 yrs time).There were 66 flats and all 64 flat owners together signed POA.But 2 flat owners were not aware,but still their flat was demolished.Now the land is vacant.Problem is now almost 4 yrs,no work started,builder not responding..When we approach new builder,they insist upon cancellation of POA given to old builder and also no objection.Problem now is unable to putting 66 owners together.and some have even died and some are out of country. Now as a single owner what best can I do? I have lost my old flat which is demolished and I am unable to do anything with the vacant land as it belongs to all 66 and where and how can I build anything?Moreover some suggest if we file a case against these big people it might take 20 to 40 yrs too by that time we may be here in this world Not sure what can be done.Kindly help.I am helpless and directionless