I always wonder about how that would be figured out- if everything had been storyboarded, if locations were already prepped/whatnot- if it wasn't severely rewritten, would it have been pretty fast and smooth to where one could feel like there wasn't that much to complete? (outside of reshooting Jor-el's scenes with another actor/minor reshoots?)
In other words, when one takes into account amount completed- would that include having everything setup for point and shoot? (unless rewritten by Lester's group?)
In Petrou's book......there is a reference to Donner's office which was replete with bar charts ,schematics and graphs expressing how much of STM had been shot(or yet to be shot) at the time of writing(1977).
It could be that the Niagra Falls location points may have already been mapped out during Donner's reign.
The construction of 52nd St at Pinewood must also have been pre-planned during the Donner shoot.
But I am speculating here!
In Mank's SII script there is a quasi type kitchen in the FOS....as well as a bed and recreation area where Lois and Supes watch videos of him as a kid.
In Lester's version that dining table backs up onto the section that features the bed......in effect substituting the kitchen that would have featured in Donner's FOS.
Theoretically Donner would only have had to construct that kitchen/recreation area to complete his SII as all the other FOS stuff had been completed(Lex/Jorel/Depowering/Repowering/fighting the villains).
Unless as you say, Donner substituted Brando's scenes with a new actor(or with York)......then that would have necessitated having to rebuild the FOS in it's entirety....as Lester did.
It's possible that Donner's team had already figured out where they would shoot in Washington.....as Spengler, the US location manager and Donner himself, had gone to the 70mm IMAX to watch a film about flight(this was where they came to the decision to shoot in 35mm only.....as 70mm was deemed to be too expensive).
The major beef I have with Lester is that he stopped Donner from continuing to shoot SII at a critical juncture.
Just imagine if Donner had filmed all the Niagra and Washington stuff...........it would have been way too expensive to reshoot it all again(so as to deprive Donner of his credit) with another director.
So the decision to halt Donner in his tracks for the SII shoot......was cold and calculating.
They knew that not enough of it was completed......to make it cost effective to shoot the remaining scenes with another director!
In Petrou's book....it says that Donner enthusiastically agreed to the moritorium on SII.
But in hindsight I think he knew that they had ulterior plans to ditch him after STM was released.
As for STM....it definitely is not just a classic super hero movie......but a classic movie. Period.