JL: Origins/War wouldn't work as an origin on film. Not without being heavily rewritten.
Well it's true that every story, comic or novel gets rewritten for the screen (Lord of the Rings).
However, I disagree with you that heavy rewrites are necessary, as I don't see the need for much reworking of a simple story that does what a first JL film needs to do i.e introducing the characters to the audience, and to each other.
If you watch the Fast and Furious films, which are fun, but not really great works of cinematic art, you don't need a film for each character before they can become part of the team. A JL film could work in a similar way.
Really, do we need that much re-writing to make an enjoyable, watchable film ? I mean, this is a superhero team movie, and as such, it isn't going to be Shakespeare or the Godfather/Citizen Kane of superhero films.
If the characters are well done and likeable enough for us to care about them and the action is well-paced and exciting, then what else do you need ? It's the interaction between the characters, particularly Green Lantern and Batman that makes JL Origins so much fun. If they pull that off well on-screen, then the movie will succeed - a detailed complex story just isn't necessary.
MOS doesn't really have a particularly complex plot, but it's awesome, and even The Dark Knight when you think about it isn't unfathomably complex, its the characters that make it such a great watch.
Avengers was pretty damn successful, and it's plot was essentially.
"Loki stirs up ****, Heroes meet up and argue, aliens invade, heroes team up to defeat them."
JL Origins/War is pretty much " Heroes meet up while investigating, argue/fight, Darkseid shows up, heroes team up to defeat him."
As long as the characters are well done, what else do you need ?
IMO very little.
So I respect your opinion but have to agree to disagree on that one.