An editor friend of mine once defined one of the difference between a DP and an editor. He said : As an editor I can screw around with my material all day and if it isn’t working I can hit the “undo” key a bunch of time and get back to a place I like better. DP ‘s don’t have “undo” keys like editors, if they undo, its all real time undo, – move the key light 5 feet left and 3 feet back. This is why DP’s get paid the big bucks ”
Unfortunately if you didnt get the image right in camera the first time, no plug in will save your focus issue. I can pretty much guarantee you the first person that creates a plug in that does refocusing in post in post will make a fortune or two.