Instead of focusing solely on the complexity of the thing you change. Include the context around what you are changing also.

This allows the Change Impact formula to differentiate between two different files of the same length. One is a complex god class with high CC. The other is an entity module that is simple but just has a lot of methods due to properties. Adding to the god class really should warrant a refactor. Adding to the entity class is just another field to store for the entity. The Change Impact formula can differentiate and point to the god classes.