Justice Society / All-Star Squadron would be my first choice.
Although a Batman Noir sounds more likely to ever happen... (Even if I'd rather a Martian Manhunter Noir, exploring his past as a private eye, pretending to be human!)
Superman
Batman
Flash
Green Lantern
Green Arrow
The Question.
Doom Patrol
Other.
Justice Society / All-Star Squadron would be my first choice.
Although a Batman Noir sounds more likely to ever happen... (Even if I'd rather a Martian Manhunter Noir, exploring his past as a private eye, pretending to be human!)
A Batman period piece because I never will be satisfied with what I've got so far:
Gotham Noir by Brubaker
New Frontier
Batman/Shadow
Dark Horse's Lobster Johnson is by far my favourite take on period piece Batman
I agree with a lot of the posters that DC has a ton of characters that could work better in period pieces closer to their original creation.
I voted Superman simply because having the guy from Action Comics #1 back when being able to bounce bullets off him was impressive and there were clear cut bad guys like Nazis works better than wondering about why no one is using facial recognition or satellites to track down the secret ID.
Batman in the 1930's-50's could benefit from having detective skills before Google, 1950's level tech (as opposed to guesses at 2020 cutting edge stuff), and a pre-Miranda warning society.
As someone else said both Ollie and the Question work better in an earlier period where their social values had more obvious targets.
Hal Jordan works better in the Space Race era with his test pilot origin.
Martian Manhunter works better in the 1950's with both the Red Scare and alien invasion fears .
I voted Other because I think any of them could work. IMO, Superman would do best in his pre-WW2 original setting, but most of the others could fit almost any 20th century setting. Some, like Batman and Green Arrow could fit virtually any era.
Kind of interested to see why the proposed Supergirl movie would take place in the 1970s. I guess the idea would be no one would ask where is Superman? Because he hasn't been born yet or is still an infant?