yes but they could have done like south ferry before they abandoned that station as well. they could have put boarding ramps were there were gaps between the doors and the platform. they also could have like i said moved the station to the beginning of the loop were the 6 line diverges from the 4 and 5 lines. the station would start at the end of Brooklyn bridge station then end the station connecting it to the city hall station get what I'm saying?
As far as I know, City Hall was the first IRT subway station built. However, SF is a different story. Again, according to my sources; correct me if I'm wrong please. SF only started with the inner loop which can accommodate 10 cars, but only for the middle door. The outer loop platform was later built; the track was already in place. I also believe that the outer platform of SF was built much, MUCH later than City Hall, thus having the technology of moving platforms.