I agree with everything that is said above. In addition, I think there should be a re-evaluation step which happens once the project has started to make sure that the way everything was planned is working out and that nothing needs to be changed. For example, during re-evaluation it may bring to attention that there was too much work put on the resources and the team needs people or that the work breakdown needs to be adjusted. No matter how well-planned out something is, things can always go wrong and by planning a re-evaluation step on a specific date, small problems can be caught and adjusted before they turn into large problems.