I have a dejavu feeling when reading [What to do about a 11000 lines C++ source file?] post, but I don't think I can start taking action on my own since I do not have the authority to take action. So I think the first step is to convince people in the organization that big lump of code is bad.
I have a similar situation where there is a single class with 11975 lines of code and every time there are new features, there is a high probability that this class will get bigger and bigger.