Direct reports are not an absolute requirement for function management. The timing question is whether a clearly defined essential function, senior discretion and credible execution support exist under the applicable filing framework.
Choose a factual milestone
If the beneficiary currently performs most operational work, identify what must change and when those changes will become real. An established-office case cannot rely on an unsupported future management role. A new-office case requires a documented first-year plan.
Do not schedule relocation solely around a new title; allow time for counsel to test the actual structure and for the government and travel stages. Choose a milestone that a document can prove. A function's scope becoming settled, an authority schedule being approved, or a policy taking effect are all events with records attached; a manager feeling ready is not.
Identify which of the facts you intend to rely on already exist and which are expected, then decide whether to file on the present position or wait for the expected ones to become actual. Filing on an anticipated structure is the more common error, because it produces a petition describing an organization that does not yet exist. Allow separately for the steps after a decision, which differ depending on nationality and where the employee will apply.
Announcing a transfer internally before the immigration basis is settled tends to create pressure that the evidence then has to absorb.