"He was always meant to be compromised," Weitz revealed. "In Gary and my versions, he was severely compromised..."
"He was a double agent," Whitta added.
As it turns out, Cassian's reason for being a spy was going to be explained with an unexpected connection to Saw Gererra (Forest Whitaker), who had apparently killed members of his family.
"For a long time, he was working for the Empire," Weitz explained. "I think this was a rationale that I added in, was that he had lost people who had been killed by Saw Gererra. And all he wanted from the Empire was the go-ahead and the ability to kill Saw Gererra, rather than Galen Erso. And that kind of transmogrified along the lines - post-me and Gary - into a Rebel intelligence officer who had done terrible things. And here, he chooses not to."
"He was a rebel soldier who was secretly working for Krennic," Whitta continued. "But then, as he grew closer to Jyn and realized that the Empire had built this weapon, he's like 'I never signed up for this! I didn't sign up for killing planets!' He has a change of heart, and flips to the Rebel side. But that's after he's exposed as a spy. And at that point, in the third act, he kinda has to win Jyn's trust back. That was all fun, that was all interesting. I think they actually shot some of that stuff early on. But I think this version ended up being more nuanced and more interesting."
It's definitely interesting knowing what the original plan for Cassian was, and it begs the question of it and how it would have impacted fans' responses to the character. Either way, we're going to get Cassian's backstory in an upcoming Disney+ prequel series, which will add a whole other level to what we think we know about the character.
“The thing I can tell you, and it’s a nice challenge and it’s a great way to approach a show, but what happens when you already know the ending?” Luna shared in a recent interview. “Then it becomes about the story. Everything is in how you tell the story and how many different layers you can find. This can’t be a show now where at the end we surprise you with like, ‘Oh no it wasn’t him!’ We’ve already seen the ending.”