The real risk here is the shape of the resourcing curve, and it catches almost everyone.
You have internal people, and they are the right long-term answer. Ramping them up takes time you do not have right now. But staffing permanently for the peak leaves you overstaffed the moment the peak passes, and nobody wants to be the person who hired six people for a surge. So the honest design is a curve rather than a number: external capacity arriving at a moment's notice while your own people ramp, a delivery rate high enough that the queue actually shortens, and then a deliberate handover as your team comes up. Later, when something important lands that should not wait, the same capacity comes back for the bump without you hiring against a temporary spike.
The other two hold throughout. Speed cannot cost quality, so a lightweight build standard comes first, empirical rather than doctrinal. And advice does not substitute for capacity, so this situation always comes with hands: we build while your people validate and adopt, and no internal development is required to go faster.