Which is bullshit. Not every film needs a light tone. This film was pitched as a war movie. They probably got exactly that and after the BvS fiasco changed their minds.
The Suicide Squad reshoots were more worrying, as they were taking place less than three months from the release date. With this film still 6 1/2 months away from release, I'm giving them more the benefit of the doubt. Reshoots are always scheduled for these huge films; it's when they come and when the release date starts to get fluid that worrying becomes valid.
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"I'm not smart so much as I am not dumb." - Harlan Ellison
I hope not. The entire point of this film was to be a war film. For me, it's part of the appeal giving us something very unique from the rest of the SW films.
It's likely most if not all of these spy characters for the rebels die. They - Disney - knew what they signed up for. Surely they know being too serious and dark has never hurt Star Wars in the past; it's what's helped raise it's reputation as a great saga when it does.
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"I'm not smart so much as I am not dumb." - Harlan Ellison
Suicide Squad was aparently having problems with the 3rd act (in line with most Will Smith films). Plus probably reacting to the reception of BvS.
But for Rogue One reshoots of 40% means Disney just didn't like the film that was presented. Doesn't mean it was bad, just that Disney were not satisfied with it.
Shame as this is the first one to star completely all new characters. They will stick to the old school characters if this doesn't work.