I wouldn't mind seeing a Nolan-esque reboot of Supes in terms of really going back to the source material to find stories and exploring the human elements, etc. in the Superman story without potentially besmirching Supes character (ie. SR).
But I don't think a lot of flashbacks are necessary. The origin can be told during the opening credits. One of my favorite examples of this was Blade 2, where Blade quickly tells you what happened in Blade 1, well all the stuff that was relevant.
For inspiration, I think they should combine Byrne and Waid's origin books. They should also look to STAS for inspiration about how to remake Supes villians. For the most part, Parasite, Metallo, Bizzaro, and Brainiac all were improved based on their cartoon depictions. They also did a good job with Jax-Or, Mala, Mercy, Livewire, Toyman, and Luthor of course. The only one I don't think they quite got was Doomsday.
I don't mind seeing a story of a young Superman first bursting on the scene, but I don't think we need to see Clark as a teen, growing up. We've seen that in the Donner film and on Smallville.
One other Nolan-esque thing I would like to see is multiple villians spread organically throughout the film. Nolan just made it work. It never felt so over the top and it helped make his Gotham feel alive. There was a degree to the focus on the villians, but so far the two Nolan films have a had a lot of bad guys in there and it hasn't seemed like overkill.
I wouldn't mind seeing a Supes movie were he takes on Intergang perhaps for starters and winds up having another threat to fight later on, one he can really duke it out with.
But I caution that Superman shouldn't be too grounded in reality. He is a sci-fi character and trying to make him too real cuts out a lot of his best villians, like Darkseid. I say make him relatable, but not to the point that he's unrecognizable.