enabling an organization as projects expenditure and project manufacturing organization after doing

We are enabling a new operating unit in an existing legal entity in Germany BU. As of now client team does not have data regarding projects hierarchy. However they want to make sure that in future there should be possibility to enable projects and PJM in this organization. I have a few questions regarding this: -

 1.       Can we enable an organization as projects expenditure and project manufacturing organization at a later point i.e. after transactions have taken place in the organization?

2.       If answer to first question is N0, then If we enable PJM attributes without adding organization in Projects hierarchy, will it have any negative impact