Here's an example of a film studio taking a film away from it's creator and probably saving it.
The writer and sort of director Elaine May filmed a story about a selfish rich man who finds himself broke from overspending. He devises a plan where he will marry a rich clueless woman so he can maintain his present lifestyle. Walter Matthau plays the broke playboy who sets his sights on a professor of botany. May's character is a real klutz and the film is about their marriage.
On to the good stuff, Elaine May went 3 million dollars over budget and after a year of editing delivered a film that was 3 hours long and had Walter Matthau murdering 2 people. Paramount took the film away from May and cut it down to it's present length of under 2 hours and eliminated the parts with Matthau killing people. It's hard to blame them. The film is essentially a funny and pretty good natured comedy and having one of your lead characters start killing people off towards the end of the picture would have seemed pretty jarring.
Walter Matthau is as usual the master when it comes to performing comedy. Elaine May is also very good as his goofball wife.
A New Leaf is a good picture but I doubt a 3 hour running length would have ever worked for this film.