Someone should write a book on the topic of telling sales "no!" 🙂 How often do they add that additional discount? I feel like that breaks whatever you are trying to accomplish with the above regardless. I have seen the same many times but always handled a little differently - I would probably advise against scripting unless you really have no way around it - the reason for this is the complexity of the ARM bundle, it has many touch-points and self-contained it handles changes to transactions and related tasks quite well - this you do not want to break so it requires some special attention if you customize. I would do some scenarios in a sandbox with everything from discount items to additional fields and see how far I could get.