The appropriate sequence depends on the actual facts and legal requirements; there is no universal answer based only on the desired moving date.
Expose the dependencies early
Provide the transaction terms, effective dates and proposed employment arrangements for assessment. Do not rely on an application strategy based on facts expected to change without reviewing their effect. Keep new-office milestones and family commitments visible in the same planning exercise.
For a petition involving an already-operating qualifying U.S. entity, initial L-1A approval periods are typically longer than the one-year period given to a genuinely new U.S. office; the exact validity period depends on the petition and the evidence of the U.S. operation submitted. The company needs to prepare evidence of the proposed operation itself, not just the individual and the corporate relationship, and that means reviewing premises, staffing, and financial capacity before treating a planned launch date as a guaranteed immigration outcome. L-1A still requires one continuous year of managerial or executive employment abroad in the preceding three, a qualifying parent, branch, subsidiary or affiliate relationship with continuing foreign operations, and a proposed position that is chiefly managerial or executive.