Sooner or later you have to decide on whether change happens as a big bang or a series of smaller changes. The theory that we all know is that change is hard and people dislike change. The problem is that the theory is wrong. We all like change IF we think it is good for us otherwise we would still be living with our parents or eating the same mayonnaise as we did when we were children (ok, I am guilty).
Big Bang? If you haven’t sold the change and therefore those that will be impacted don’t believe it will be of value for them . . . I would consider the big bang approach. In the big bang approach you have a chance to get all of the changes in place before resistance can solidify.
An incremental approach make sense when you can use one change to sell another. This approach works best when you spend the time and effort needed to sell the value of the first few changes and then let the results prove your integrity.