We developed an application that needs to be customised for every new customer. Customisations include gui layout, enabling or disabling actions that customer can execute, adding or removing fields on forms, and lot of other things. Everything I mentioned already can be achieved using our config files, but I'm not satisfied with time we spend maintaining those files. Although I would like if someone with experience could give me some hints, I understand that this isn't a trivial question. So I'm asking if someone knows about the book that deals with those issues.