The lead-up to Justice League's release saw Warner Bros. repeating the mantra that the movie was still Zack Snyder's movie, even though he'd been replaced by Joss Whedon. We now know that he was actually fired, but at the time the message was that Whedon was merely completing Snyder's vision and adding some dialogue.
It wasn't until the movie came out that it became clear that a number of significant changes occurred behind the scenes, adjusting the tone, trimming the story, brightening and over-saturating the lighting and colors, and more. While a number of these changes are fairly obvious from wonky blue screen and out of place jokes, the ones that get the most attention at the changes to Superman. Thanks to Henry Cavill's mustache and it's poor CGI removal, it's really easy to spot which Superman scenes come from Whedon and which come from Snyder, with the former accounting for accounting for around 90% of the Man of Steel's screentime.
While characters like Cyborg, Flash, and Aquaman merely had cut backstories, Superman's story and surrounding scenes were almost entirely replaced with new scenes. So what was Snyder's original plan for the character before Warner Bros. decided to have Whedon execute a total redo? The full Superman story from Snyder is difficult to gauge without an actual release of the "Snyder Cut," but a combination of behind the scenes footage, photos from deleted scenes, and other details have given us a good idea of Snyder's original vision for the resurrected Man of Tomorrow.
This Page: How Superman Was Brought Back From the Dead
The Whole Justice League are Grave Robbers
The differences that have been revealed surrounding Superman's resurrection begin with the collection of his body. In the movie we only see Flash and Cyborg exhuming his body, with a little back and forth bonding time where they realize they're both "the accidents," considering the origin of their powers. While the movie makes it appear as if this is a mission mounted solely by the two youngest heroes, Zack Snyder has posted a behind the scenes image proving at least Wonder Woman and Aquaman were also meant to be present (with many assuming Batman was driving the van)
While the actual digging was likely still performed by Barry and Ray, the presence of Diana and Arthur shows there was at least more connective tissue, making the collection of Clark's body more than just a cutaway scene, which is ironic considering Whedon's involvement was originally cited as participating in rewrites to add connective tissue, yet that's ultimately one of the biggest things lacking from the movie.
The Mother Box Resurrection
The actual mechanics of the resurrection were likely fairly similar, with the Mother Box acting as a sort of cosmic defibrillator, but there's clearly a significant amount of missing context. How did they come to know that was a viable idea? Batman isn't exactly one to say "let's try electrocuting a dead body and see what happens?"
The most likely explanation is that the Kryptonian Codex inscribed into Kal-El's body was somehow relevant. In interviews before the movie's release, Ray Fisher said Cyborg has access to vast knowledge of the galaxy due to his fusion with the Mother Box, so he likely has an understanding of Kryptonian physiology and knows how to use the Mother Box to jump-start the whole resurrection process.
One of the leaked deleted scenes featured Cyborg learning the history of the mother boxes and delving into their full capabilities (which is traditionally an unlimited scope), so it only makes sense that it was him - not Batman - that came up with the idea. The fact that the dialogue with Bruce Wayne coming up with the plan is visually clearly a reshoot only supports that assertion.