As soon as you have confidence, start developing
As soon as you have confidence about some project direction, start developing areas in which you have high confidence.
This pattern can increase rework, but it is more in the spirit of piecemeal growth architecture than would be a master-planned system that precipitates from "complete" requirements. It is likely that any false starts will also be educational at the enterprise level. In fact, as a risk management measure one can consciously decide to not commit to the results of such an activity. On the enterprise level, this becomes the pattern SkunkWorks; with a project, it could be BuildPrototypes, or where ConstantRefactoring and its supporting techniques enable cheap rework, it becomes EarlyAndRegularDelivery. In any case, it is better to be learning lessons than to have workers sitting idle.