I agree that all the parts are very important, however, I have to disagree with you on this point, that the communication management plan is the most important part of the DDP. Not that there is more important part, but my reasoning is that without any of the other parts, the project will fail, and I can’t see the communication being more important than the say the scope. If you don’t know what you are suppose to design, how can you communication to workers or stakeholders about schedule, progress, etc.

Thanks
Adrian