Good point. As a "whodunnit" I don't think the film will work that well. Unless they decide to spice it up and mess with the ending for the sake of "drama"- Probably why the earlier scripts had this element. I am under the impression that Hollywood loves to jiggle with storylines in vain attempts at bumping up the wow-factor.
But the book isn't really a whodunnit, is it.
Most of why we read and re-read the story is the enormous amount of visual/verbal material in there. The amount of narrative – if transcribed in the form of text – would be staggering. All those visually linked, threaded plotlines, all those small hints giving extra depth and info make for a gread read, over and over.
I understand that some directors would balk at the idea of encompassing its volume. The average audience would be coming out of the cinema with a migrane and a bursting bladder.
Maybe Snyder is floundering way over his head. Maybe he feels that if he goes for key dialogue and nicely shot set-peices he's home and dry. If I were him I'd be going hell for leather to use the cinematic toolbox to the max to get the film working hard enough. Maybe he's doing just that. Cool job the guy has!
As for visitors unaware of the basic plot-line. Well, I guess a warning or two on the main page should be enough. Though I would be very interested to read the source material before going any further in on this kind of web-site. I wonder what I would have made of it today after a first read?
A lot of big-budget films are based on events of which the outcome is already known: Apollo 13, Titanic, Lord of the Rings all worked reasonably well despite the threat of the audience "knowing" how they ended.
Watchmen will be more of an exercise in how the filmmakers translate the guts of the story to film. I will not be very upset if they fiddle with the details, as long as the film demands further viewing. Just like classic movies should.